I made at least four mistakes when I had solar panels installed on our 32'DP:
1) I thought I knew enough about solar power.
2) I thought the techs and solar "professionals" knew what they were doing.
3) Had a professional (RV Tech) install 2 80 watt panels, with wiring capable of carrying at least twice that. Wire not really adequate for upgrading as a I later found out. See item 2.
4) Had a professional (Solar installer) add 2 130 watt panels and new controller. See item 2 again.
Now I need to seriously upgrade the wiring AND move the controller roughly 25 FEET closer to the batteries!!!!! :S
Listen carefully to the advice of the many experienced and knowledgeable people on this board. With their suggestions I was able to improve the system significantly until I can get home and rewire.
I would also suggest that if you don't go bigger at the start, be prepared to do so later and make provision at the start.