You shouldn't farm until you get your bonus up to at least 150%. The early game is meant to progress a certain way and KEM farming can cause problems.
Read the following
https://forums.ea.com/en/the-simpsons-tapped-out/discussion/90074/tips-for-players/p1
https://forums.ea.com/en/the-simpsons-tapped-out/discussion/149536/kwik-e-mart-also-known-as-kem-farming-guide/p1
It's a town not a base
Don't ignore Krustyland
Only buy land when you absolutely have to buy it
Do Springfield Heights for the bonus
Buy the beach hideaways and upgrade then ASAP
The Burns box has unique items in ti and then it is the best way to up your bonus. Next would be Jet engine bikes in the vault