Energy - Bolts of lightning, used to enter Adventures and other types of levels. Each player has a recharging cap tied to their Portal Master level, but more can be obtained over the cap from other activities - however, the level will never recharge past the cap on its own.
Gears - Tiny Gearbits, used to enter Arena battles(and not Private Matches, which are free). Each player can only recharge up to 5 Gears at a time, but more can be obtained from events or the main Shop. As with Energies, gears won't recharge past their cap.
Gold - Golden Chompy coins. They are used to purchase some items and any upgrades to Skylanders. The treasure can be obtained from nearly every level in the game, though bigger quantities come from the Cave of Gold.
Gems - Rare, purple precious stones. They are the main method of summoning Soul Stones at the Spring, but can also purchase a variety of items at shops, reset boss levels, and recover health at the Realm of Souls.
Arena Medals - Golden star-shaped medals, obtained as rewards for battling in the regular Arena. They can be used to purchase items at the Arena Shop.
Guild Points - Also called Guild Medals, they are round medals, obtained as rewards for engaging in Guild activities, such as donating Soul Stones, completing Guild Missions, and participating in Guild Invasions and Guild Wars. They can be used to buy items at the Guild Shop.
Chaos Coins - A coin with The Darkness' sigil, used to enter Standard rifts in the Hall of Chaos. They are obtained in a single Weekly Mission, and can be used to enter the Hall when all free chances have been used up.
Extreme Chaos Coins - Purple versions of the above coins. They can be used to enter Extreme rifts when all free chances are used up, but there are no methods to obtain them at this time.
Episode Dungeon Coins - Custom coins with Spyro's stylized face on them. They are currency obtained only in these dungeons and used for the Episode Dungeon's Exchange Shop, and reset every time a new one is opened. Nightfall's currency were the dark grey Dark Stones, and Drobot's were the orange Symbols of Knowledge.
As Gearbits were used as currency by scavenging during the time of crisis during Skylanders: SuperChargers, it is possible they are used for Arena battles instead of Vehicles because there is no longer a need to compensate for transportation and essential resources.
Gems, Wish Stones and gold were used in Skylanders: Lost Islands, but in that game, gems were green, and Wish Stones still had their old appearance.