From my experiance.

Find friends in your league and in cup,champions league (one's that watch the games)

After a little while you will get to know these teams and there squads... now this is where i would say to be smart look at the managers that are above you and try and put negotiate on there players at the end/start of the season as they will be looking to get a better squad.

The best way to get tokens/packs is to switch between topeleven.com & via facebook topeleven site via your Pc,Android,ios device rotate between them and reap loads of tokens & Packs. You could buy tokens but for me that is the easy way and not as much fun.

In regards to building a team i still have players from 3 seasons ago and they are still an integral part of my squad.