This obviously depends on the buy-in amount of the player, but generally you should have several chips equal to the size of the small blind & big blind and larger chips that are commonly used for preflop raises and bets on the flop & turn. For larger bets, people can use bigger chips such as 100USD chips in a 1/2USD game and announce how much they want to bet.
As a practical example, in case you host a 1/2USD Holdem game, you could give a player buying in for 200USD (100 big blinds) ten chips worth 1USD, five chips worth 2USD, 16 chips worth 5USD and one or two larger chips worth of 50USD or 100USD.