The first thing that you need to do in order to start a pokemon library, is to go on and watch the entire show. You need to start by watching the very first episode, and then go on and watch as many episodes as it takes, for you to truly understand and comprehend pokemon completely.
After you have gone on to watch ample episodes of the cartoons, you will get a good idea over just which pokemon are rare compared to the others. This is going to help you look for these cards when you are collecting. The rarer the card, the more value that it has. So make sure you only try and get the ones that would have a much higher resale value.
Try and trade your way up and look to get first edition releases of cards. This is always more helpful and makes sure that your collection is way better as compared to everyone else.
If you are done collection cards, you can go on and get some other memorabilia as well. Now these are usually released in a limited amount, but should you be able to get your hands on some of these items, you can go ahead and sell them for a whole lot amount of money in the future.
However, when looking to buy memorabilia, you need to ensure that you don't end up buying any fake items. A lot of times, knock off products are made and sold instead of the real ones, which is why you need to distinguish the fakes from the real ones.