No video; just...pay attention! Helps to use 2 players, and play on an easier level (shorter = better). Make sure to go thru ALL the trees for the random drops, those count. Avoid selling towers, and especially avoid levels that have water. You don't have to rainbow, so keep it simple!

This one is dead simple, but I recorded it anyway. Use the Easy-3 level, where you start with 2k gold, and build, you can even pace yourself...not hard at all!

I used the spiral stage from 'Black Flag' because it has smaller waves of enemies. Save up 5 gems from the first few waves, then bomb the group of six spiders. DEADLY EASY!

This one took a few tries to time it just right. I used Hard-1, wave 6 or so to get mortar(s). I accidentally built a 2nd mortar, but it turned out well.

and from Pyobum, a strategy I'm willing to say is better for 1 player (Thanks!)

and from AstralBlades 

I don't really need a video to explain this, just use the 4-tree level. Upon starting, head for the trees. The logic is there are 3 coin drops and 1 gem drop (4 total) which all have to be released from THE SAME tree. If you get ANY drop which is not 15 coins and a gem, retry the level. Takes 10 to 50 tries.
Odds of getting it on ANY tree is 1/4^3, but you get 4 tries per load, so 1/(64/4) = ~1/16