The two main aspects you should focus on when buying a wallet are functionality and presentability.
What do we mean by functionality?
Your wallet should allow you to carry a good amount of cash. Moreover, you will probably need to bring some credit cards, an ID card, business cards and photos.
What things should you not put in your wallet to optimise space?
Discount cards, medical cards, coins, receipts and social security cards are all items that can make your wallets too heavy.
What kind of wallet should you buy?
First, you need to understand your need. If you are a businessman or an employee, a classic bi-fold wallet is always a good choice. It usually features a spacious note compartment and some card slots. Probably if you have several bank accounts, you might consider going for a cardholder rather than a bi-fold wallet.
Moreover, if you are a gym guy, you might consider getting a tri-fold wallet, which usually features a coin purse, zipped compartments, multiple interior card slots for your gym membership card or any other memberships you can have with other supplement retailers.
Focusing on presentability, I recommend you get a true leather wallet if you want both to look stylish and have a good quality item.
However, if you need a tri-fold wallet for your gym time, you can buy one in synthetic materials as well. In the second case, I will look for a waterproof wallet if you could spill some liquids over your wallet.
Understand your need and choose a stylish wallet to complete your outfit!