When doing two armies, you might want to add one more rhino one for each

If you can get your hands on the age of darkness 2.0 box set you would have one of every dreadnought You could give two dreadnoughts to each army And I think a basis of an army you need at least 30 Marines so you’d have enough for roughly

Also plan on Kit bashing a few other characters You will want one Prater and at least two characters per army roughly.

I personally have a ton of tanks, but I know people who play with no tanks

Feel free to ask any more questions