I need help (in game)

It’s around day 15 I’m Spain doing good, have around 16 cities so I have a stable economy right now, I wanted to try something new so I researched tanks, gunships, attack subs, and mobile aa. I want to research artillery but I don’t know if I should just research towed artillery for costal batteries, or research both artillery and Mrls. I’m all over the place right now and honestly need advice