Don't worry about losing rest/treatment packs - you won't. Although they will certainly come in useful as you progress and are playing two games a day and your players become tired. Sometimes your league and cup games are scheduled quite close together and if both games are away from home you are unable to reschedule games. It costs two tokens to reschedule a home game to a different time.

As for your transfer policy, everyone has a different way of playing the transfer market. Over time you will come to decide what is the best way for you. I was lucky when I started as I got promoted in my first season with quite a poor team and with several players retiring at the end of that first season. I invested some real money into the game to be able to buy a couple of scout players so now I have a good solid squad.
Don't feel you have to invest real money though, as my friend joined at the same time as me and hasn't invested (but has built up tokens and health packs through watching videos) and we have both progressed through the leagues together and are now at level 4 - although we are on different servers.

* edited to add a missing word!