Given a reference text about Magic the Gathering decks, please suggest cards I should consider in a Midrange deck.

Most classifications of Magic the Gathering decks begin from one of four major strategies: aggro, control, combo and midrange.

Aggro
Aggro (short for "aggressive") decks attempt to reduce their opponents from 20 life to 0 life as quickly as possible, rather than emphasize a long-term game plan. Aggro decks focus on converting their cards into damage; they prefer to engage in a race for tempo rather than a card advantage-based attrition war. Aggro generally relies upon creatures as its accumulative source of damage. Aggro decks can quickly overwhelm unprepared opponents and proceed to eke out the last bit of damage they need to end the game. Aggro decks also generally have access to disruptive elements, which can inhibit the opponent's attempts to respond.

Example cards: Savannah Lions, Bitterblossom, Lightning Bolt, Rogue Elephant, Incinerate
Example decks:
White Weenie, which uses small, efficient creatures such as Savannah Lions, Icatian Javelineers, and Mother of Runes
Affinity, which uses the affinity mechanic and large numbers of artifacts to quickly play spells such as Thoughtcast and Frogmite, while efficiently dealing damage using Disciple of the Vault and Arcbound Ravager.
Zoo, which uses low-cost, high power creatures such as Tarmogoyf and Wild Nacatl to kill the opponent quickly.
Sligh, which utilizes its mana as efficiently as possible to kill the opponent quickly, using low-cost cards such as Jackal Pup and Lightning Bolt.
Suicide Black, which uses efficient but dangerous cards that cost life such as Thoughtseize, Dark Confidant, Grim Tutor, and Bitterblossom. Suicide Black epitomizes Black's philosophy—win at all costs—and treats even its life total as an expendable resource.
Control
Control decks avoid racing. They attempt to slow the game down by executing an attrition plan. As the game progresses, control decks are able to take advantage of their slower, more powerful, cards. The primary strength of control decks is their ability to devalue the opponent’s cards. They do this in four ways:

Answering threats at a reduced cost. Given the opportunity, Control decks can gain card advantage by answering multiple threats with one spell ("clearing"/"wiping" the board), stopping expensive threats with cheaper spells, and drawing multiple cards or forcing the opponent to discard multiple cards with one spell.
Not playing threats to be answered. By playing few proactive spells of their own, control decks gain virtual card advantage by reducing the usefulness of opposing removal cards.
Disrupting synergies. Even if control decks do not deal with every threat directly, they can leave out whichever ones stand poorly on their own; e.g., an enchantment which gives a bonus to creatures will never need attention if all enemy creatures are quickly neutralized.
Dragging the game out past opposing preparations. An opponent's faster, efficient cards will become less effective over time.
Example cards: Force of Will, Duress, Wrath of God, Pernicious Deed, Void
Example decks:
Tezzeret Control, which controls the game using counterspells such as Mana Drain, builds card advantage with cards such as Dark Confidant, and ends the game using Tezzeret the Seeker to find Time Vault and activate it for infinite turns.
Mono Blue Control, which uses a heavy suite of counterspells alongside card-drawing such as Thirst for Knowledge, removal such as Echoing Truth, and a win condition such as Tezzeret the Seeker. This class of deck is nicknamed "Draw-Go," because most of its players' spells are instants designed to be played during his or her opponents' turns.
Blue-White Control, which is similar to Mono-Blue Control, but features more board-control cards such as Wrath of God, and Pacifism.
Psychatog, supplemented by card-drawing like Fact or Fiction and a number of disruptive spells.
Astral Slide, which uses large numbers of cards with cycling, including those with added benefits such as Eternal Dragon and Slice and Dice, to power Astral Slide and Lightning Rift.
Mono-Black Control, which uses removal spells such as Innocent Blood and Barter in Blood to control the board, and Cabal Coffers to kill the opponent with spells such as Consume Spirit. It can also use cards like Underworld Dreams to put the opponent on a timer.
The Deck, which uses card drawing such as Fact or Fiction and deck searching cards such as Demonic Tutor to find powerful cards that are highly effective against particular strategies (such as The Abyss, Diabolic Edict, and Balance), alongside a Blue base of counterspells to control the game and obtain an insurmountable lead.
Combo
Combo decks use the interaction of two or more cards (a "combination") to create a powerful effect that either wins the game immediately or creates a situation that subsequently leads to a win. Combo decks value consistency, speed, and resilience: the deck should be reliable enough to produce the combo on a regular basis, the deck should be able to use the combo fast enough to win before the opponent, and the deck should be able to withstand disruption and still win.

Many decks have smaller, combo-like interactions between their cards, which is better described as synergy.

Example cards: Flash, Tendrils of Agony, Empty the Warrens, Aluren, Painter's Servant.
Example decks:
The Perfect Storm, which utilizes Dark Ritual and artifact mana to draw cards and fuel a lethal Tendrils of Agony, all the while disrupting the opponent with Duress and Force of Will.
Painter Combo, which uses Painter's Servant and chooses Blue to permit Red Elemental Blast to destroy any permanent or counter any spell, while also allowing Grindstone to put the opponent's entire library into their graveyard.
Worldgorger Dragon Combo, which revolves around the infinite loop triggered when Worldgorger Dragon is animated from the graveyard using an enchantment such as Animate Dead. The loop generates mana and card drawing which is then used to end the game.
Belcher Combo, which uses free and efficient mana acceleration to play and activate Goblin Charbelcher, preferably on the first turn. Because the deck has two or fewer lands, one activation of Goblin Charbelcher will almost always kill the opponent.
Hulk-Flash, which is dedicated to casting Flash and putting a Protean Hulk into play and then into the graveyard, allowing the player to find a combination of creatures which will kill the opponent instantly. Summoner's Pact and Merchant Scroll are used to find the combo pieces, while Force of Will and Pact of Negation protect the combo.
Steel City Vault, which uses "Draw 7" spells such as Timetwister to rapidly assemble the Time Vault-Voltaic Key combo for infinite turns. The deck also uses several cards such as Force of Will and Ancient Grudge to efficiently deal with Null Rod, the most effective answer to the Vault-Key combo.
Hexmage Depths, which uses Vampire Hexmage to inexpensively remove the counters from Dark Depths and put a flying, indestructible 20/20 creature token into play as early as the first turn.
Midrange
A typical midrange deck has an early game plan of mana ramp and control, but begins to play threats once it reaches four to six mana. A midrange deck will often seek to play a reactive, attrition-based game against aggro decks and a more proactive, tempo-based game against control decks. Colloquially, this is referred to as "going bigger" than aggro and "getting in under" control.

Example cards: Huntmaster of the Fells Thragtusk, Sakura-Tribe Elder
Example decks:
Jund Midrange (BRG), a powerful and flexible deck with virtually zero bad matchups thanks to the access of the most powerful cards that each color can offer: black gives Liliana of the Veil and powerful discard cards like Thoughtseize and Inquisition of Kozilek, red a reliable removal in Lightning Bolt and the green some of the best creatures like Tarmogoyf and Scavenging Ooze.
Abzan Midrange (WBG), which is similar to Jund, but trades speed for powerful white based cards like Path to Exile, Lingering Souls and Siege Rhino.
Jeskai Midrange (UWR), which has more control elements, using Sphinx's Revelation to draw into a very large number of cards and Assemble the Legion to end up swarming the board with tokens.
Temur Emerge (GUR), which leverages the Emerge mechanic introduced in Eldritch Moon to efficiently use ramp creatures such as Pilgrim's Eye and Primal Druid for their land-smoothing abilities while sacrificing them to Emerge board-stalling threats such as Elder Deep-Fiend as early as turn 4, also filling the graveyard to make Emrakul, the Promised End playable on turn 7.
Tron, which tries to build the triplet of lands known as "Urzatron" (Urza's Tower, Urza's Mine and Urza's Power Plant) as quickly as possible and then uses the massive amount of mana to play powerful cards like Karn Liberated and Wurmcoil Engine as early as turn 3.

You should consider Huntmaster of the Fells Thragtusk and Sakura-Tribe Elder