1) the one going down very very very steeply :) and yes you should give them a shit loads of money, they're really bad managers...
2)yes a few... I'd say you could add some armour and weapons to them (silver)
3) I'd say always loose italy and Africa, they're such money makers... I was able to get my finance up in 3 turns!

another I thought of is to give them bigger starting garrisons, because as I said, gaul was conquered quite easily because of 2 things;
1. I had very experienced troops walking around,
2. their garrisons could easily be only 2 units of auxilia