Quality is your best insurance when it comes to collecting. It is the single most important element to consider when purchasing. You want the best possible original condition you can find and afford. Every ding, tear, scratch or missing piece means a loss in value. Shop around for the best, for less.
Every area has bargains.
If you love photography, start with lesser-known artists' work, and be very selective in what you choose. Keep your eye on your goal and be disciplined about how much you spend. Know that you can always trade up. If it's rare, or might become rare, it's more likely to hold its value. Rarity is the hallmark of a strong art or collectible investment.