So I'm really struggling around the 1200 range. I jumped up there very quickly but it is insanely hard to get much further at this point. Usually me hovering around there or dropping to high 1000s. I'm willing to try out some different combos if anyone has suggestions. To counter Prince I use Tombstone, Musketeer for Baby Dragon, and Minion Horde for Giant Skeleton. Otherwise anyone want to offer any suggestions/switches I should make with my decks?
I'm not sure about using both minions and minion horde. Those also don't seem to go great with hog rider since he'll be the only thing their ground attackers can hit other than the occasional skeleton. I think the obvious thing for you to do is just to upgrade your cards, though. I think you've got enough for a level 7 Bomber and almost enough for level 6 Barbarians. A lot of people seem to get to the 1400s leaning heavily on level 6+ Barbs.
This may not be obvious to everyone since the numbers don't seem to go up
that much, but card level (especially for troops) is a huge deal. We're talking about compounding 10-21% more effectiveness per level, generally and depending on how you count it. The reason people do so well with level 7 Barbs and level 5 everything else is that as long as you keep minions off of them it's basically impossible to deal with the Barbs for cost.
Also note that Witch is a great counter to Prince too, so if that's all the Tombstone is for I'm not sure it's necessary.
Just started playing this game, what's the most effective way to use gems?
Easily gold. Although buying Giant Chests is actually a better deal than paying to open Silver and Gold Chests provided the Giant Chest is more likely to produce an epic. But with buying gold you get a minimum conversion of 120 gems for an epic of your choice, if you wait long enough, and likewise you have a lot more control over which commons and rares you get. Giant Chests are nice but they will tend to give you very large numbers of just a couple different cards - I just got 150 Teslas in one, for example - that you might not want.