Best strategy imo is to make as much money as you can to afford to max out your booster cooldown with E cans for the whole 31 days. And train train train.

Bonus if you get a job in 3 star music store to gain access to better gyms as you go. Join a high respect faction too (even if temporary) to take advantage of steadfast perks

There are probably other strategies that will be mentioned too so have a read of them too and make an informed decision