USA Ground RB 6.0 BR

Just got an M18, not sure what to play with it in my lineup as my other tanks are all 5.0 at most. What tanks and planes should I research and add to the lineup? Any suggestions are appreciated, thanks.

Jumbo and m36/m36b2 probably, considering you already have the m4a1 76

Should I go for the m4a2 aswell?

Yes, you can make a good lineup with m4a2, m44, m24, t77e1, and then if you have the crew slot you can add the m4 as a backup