1) I did almost the same for leveling up as you do, and it did hurt my Gold income, what I did was mostly sell all irons and use the bronze to level up, at one point this will be like natural to do because of the gold difference. I would suggest you check Lafate's thread of Frequently Asked Questions for a general idea of where to farm for specific things.

You'll be starting to move to different missions later on, it's just about patience.

2) The best way of farming affection, for your female units at the very least, is doing the Challenge Missions, as well as for fairies of different rarities.

3) As others have suggested, it is a good idea that you get Katie and Cloris, they will be good staples for some time on your team, specially Katie given that she refunds her own cost at base class, and when CC'ed, she gives you a good 15 UP. Lilia could be a good investment as a duelist, namely because she deals magic based damage and she can dish some good damage to enemies you find hard to kill on your way. Bernard and Leeanne will be your main tanks, investing on them on the long road will be a good choice until you get either Bernice or Gellius. For archers, Bashira will be a great attacker, as she is right now she shoots 2 arrows on her skill time, CC'ed she will shoot 3 which she can put to great use, being a Platinum unit though she will be little bit expensive (because she uses only silvers), Claire is a bit cheaper (she uses 2 Irons and 1 Silver) and she focuses on increasing her damage.

I guess that's all I could give as advice, hope you find it useful ^^