Army building

So I've been in the hobby a couple months now and mostly been buying what I'm interested in painting and the lore, but I want to do a deathwatch army now to play. I have the combat patrol (not so great I know, but got it before I decided to play), a veteran squad, kill team Cassius and the watch captain. From what I've read, and I'm still trying to learn stuff, I want at least one more veteran squad and maybe the watch master? Is there a website you can look at that helps with building armies? It's a bit overwhelming as a new guy, any advice is greatly appreciated, thanks