Congratulations on your recent purchases, the 150 is an excellent AB and the 180 is a fine compressor.
In answer to your questions, yes IMHO you should have a moisture trap. Compressed air tends to create moisture and the last thing you want is a drop of water splattering your paint job. The closer to the AB you can place the trap the better. You can buy relatively expensive in-line ones, but I have an "industrial" style trap mounted on my spray booth and have never had problems. I paid around $10 for mine at Princess Auto (Canadian equivalent to Harbor Freight).
As to what else you need, we would need to know what you have! Spray booth, respirators, cleaning station, and good lighting are some of the things most of us end up with. Personally I wish I had a lot more talent!