It all depends on what you are interested in, and where you prefer to shop. You may be interested in coins, and not every store has an extensive selection of coins, so make sure and do some research before you buy a product from a specific store.
If you are looking for a theory11 product, I highly recommend Distortion and Panic. Aaron's teaching on Panic is phenomenal, I mean, it is great. Distortion is an incredible, visual effect that is guaranteed great reactions.
If you need any help, PM me and I'll give it my best.
Peace,
TDA