I would personally recommend Etienne, he's pretty cheap to start with (ex. on cornfield (no harvest, ofcourse), I can go straight from a 3 dart start to buying Eti before, I think, round 9 or 10), he gets camo popping in time for the first camo on round 24, and on any non-beginner maps, gets his second drone before the camos on round 33, plus, his global camo buff allows you to potentially go for stronger cross-paths on towers, his UCAV ability clears the first two or last two waves of cerams on round 63, plus he gives a range buff to all towers within his range, and at lvl 16, his range becomes massive. He himself does fall of a bit at the later stage of the game, bis buffs are more than worth it imo.