If you're unable to build a decklist for an easy deck like Machamp, I wouldn't even bother. Just practice a whole lot more with deckbuilding and you'll eventually get it right and think of your own deck. And read the Modified section of the Beach for inspiration (do NOT copy decks).
But since you asked...
Cradily LA is a decent deck and inappropriately cheap. You need 3 Cradily, 3 Cherrim SF, 1 Uxie and 2 Claydol and that's it for rares. It is however extremely hard to play right, and therefore very fun.
Same for Drapion SF. You need 3 Drapion SF, 1 Drapion X from PT and 2 Claydol, as well as various possible lines. Again, to make this work takes a lot of knowledge, but if you get it down it's pretty fun.
For a semi-easy-but-still-fun deck to play, go for Bellossom. Get 4 Bellossom LA, 1 Vileplume LA and 2 Claydol. Probably the cheapest of the whole list I gave you. It's capable of some fast damage, but to win with it requires at least some tactics.
Toxitank is the last cheap deck I can think of. 4 Toxicroak G, 2 Skuntank G (isn't even a rare) and maybe a Dialga G and G X along with some Uxies. Not that hard to play but it's better than you'd think.