Try to find suchbot games, at start build 1 wisp fast, this will give you advantage over enemies, maximize lumber, and send units at lvl 1 if you can dino, if you can't wait till level 2 or 3, see when team sends.

send levels are usually 1,3,7,8,10,12,13,15,17,20,24,28. Rest is up to how much lumber you have.

Most likely you will start with prophet as builder that will randomize your building. for like start best is:
Archer with upgrade, sprite with upgrade, little orc that costs only 20, with upgrade, Infantry with upgrade both units are good etc.

After level 10 if you didnt win by now, focus on building siege/heavy towers that will help you with harder levels such as 17, save lumber and send together with your team...