I went straight from max town hall 5 to town hall 7 and it is really easy. I can get 2 million gold and elixir in a session (non-boosted) and that's enough to upgrade anything at th7. Over the past 2 days I upgraded half my walls from 5 to 6 and I've done 30 to level 7.
Just be sure to unlock dragons asap so that you can 3 star most th7's in war.
Well finding lower bases is still ppssible just a few days back a th7 raided me with bk and lvl 4 barbs.. I am th5
I would always max any offence,camps, spells and troops. Defences should be max or as close as possible before your need to upgrade gets the better of you. You can get away with walls as long as they are not embarrassing. Some way off yet I know but at TH10 Skulls are ok but don't go to TH10 without all skulls or pretty close in my view.