If you plan to stay in EA awhile, I recommend building a factory and upgrading it to lvl 2 before going to IA because you pose less of a target for attacks that way
I agree with Fanchon. Also, since you are looking to 5 star opponents, you need to focus on damage dealers. Heavy infantry or cannons. A sapper as well so you don't waste time taking down the initial wall
Pursuing a single leader is not always the best strategy. Each leader has research for attack and defense. Better to research from several leaders, focusing on either attack or defense research, depending on what's important to you.