Good game if a bit repetitive

It is enjoyable but repetitive. You can complete the game without ever purchasing gems using real world dollars just spend your gems wisely in the game. This game will try and get you to buy gems constantly even offering deals and it will try and convince you to pay to upgrade your characters. If you already own the action figurines then forget that and just follow my advice below.

It costs 200 gems to add a character and then 20 gems for an extra attack slot and then 25-45 to buy the attack. Then on top of this you have to spend your gold levelling the skill (costs about 66000 gold each attack skill for max).
Dont waste your gems if you already own the character figurine. Enter the character skycode that came with it but only do this once you have 100 gems ready. Once you enter the code you can purchase all the attack slots, attack types and attack skills for that 100 gems. This is much cheaper and should allow you to get about a dozen prepurchased characters into the game before you are done. You may want to have one of each element in order to access all the gold in the game but not strictly needed to finish the game. Each day an element will be featured that will give you more gold if you use a character from that element in your party of 2.

Dont waste you gems and gold on healing potions or extra attack items like the bombs or lightning. Focus on the characters, once you have a few it is better to just fight until they die and then pay between 100-300 gold to add another of your characters to the fight. Honestly this will save you a lot of gold and gems. Dont worry none of your characters really die in the game just the battle.

One more thing, gems will come at a rate of 30-60 per quest level but only the first pass through (another reason to spend wisely). After the quest level is completed you can always replay it for more experience and gold but youll be lucky to get more than 5 or 6 gems on the replay. Oh and the bonus Xmas level can be replayed for more experience at any time since the bad guys will match your experience level every time. This makes it a tougher challenge. If you want to make it easier than go to it just before leveling that way you can level after you hopefully win the first battle and then have a level up on the rest of your opponents on the level.

Good luck and dont waste you real money on gems!

the Original Nurbel about Skylanders Battlegrounds™, v1.1.0