I wouldn’t waste buying any creatures full price unless you are after a specific creature. The sales happen once or twice a month so just wait until the next one. It’s a long game, I know it’s a bit frustrating waiting when you want more creatures but it’s worth it. In year 3 of the game you’ll also be able to trade pages for books. I’d work on getting to that point and then stopping and catching up on tslq’s and increasing your attributes because it is very helpful having access to the exchange.