In level1 and 2 you normal do not need to buy a lot of player, just replace the older one for more young and with better Q, try to save tokens for the next seasons, because it becames harder.
I prefere to buy 3* fast trainers that free agents.
The Best players to buy are those with the highest MV, because they train faster.

In terms of facilitys there isen't a priority order, but those how give you something are the more important, just do not use Tokens to build faster.