This is my tried and true deck. It's gotten me just above 3800 trophies, and when I finally accumulate enough gold to upgrade a couple of the cards I expect to get even higher. There's nothing too fancy about it. There are no legendary cards, and most of the cards can be acquired early in the game. It sometimes has trouble with decks that use a lot of lightning, and I've had to develop some techniques for dealing with elite barbarians, sparky, bowler, and golem.
The mortar is integral to this deck and chips away at opponent's towers. Meanwhile, I defend it. Fire spirits are great for taking out minion horde and alright against elite barbarians when I also drop a valkyrie or mini pekka. The wizard and valkyrie take out hordes with ease, and the musketeer drops balloons and other flying pests out of the air. Mini pekka unloads a ton of damage if it makes it to the tower. Zap helps take out hordes, reset towers, enemies, and other cards with charge up attacks. Finally, the fireball is great for dealing a lot of damage in a decent sized area. Use it take out buildings and finish off towers - even better if there are some enemy units around to get hit at the same time.
This is my current golem deck. Ever since I got a golem I've wanted to make a deck utilizing it, and I think I've finally found one that works for me. It's gotten me into the 3300-3400 trophy range, but I'm hoping to get a little bit higher. Unlike my other deck, this one has more often steamrolled opponents. However, I feel like I'm at risk of being steamrolled by my opponent with this deck more often - and believe me it's happened.
The golem is pretty self explanatory. Drop it at the back, or up front, and get ready to support it. It's usually a good idea to not drop it right away - find out what sort of cards your opponent has that might counter it. If those cards are out of rotation it might be a good time to drop the golem. Meanwhile, while waiting to drop the golem defend with the log, zap, and the wizard. If something heavy is coming drop the mini pekka or lumberjack. What we want to do is get the lumberjack and golem out at the same time. That makes for a terrifying golem. This deck has been pretty fun so far - I think I want to switch out the archers for the mega minion, but I need to level it up some more first.
If you haven't given the game a try - give it a try! It's free, and though it has in-app purchases I've made it as far as I have without spending any money. Have fun, and don't be a jerk with your emotes!