Anyway, I've changed my strategy since yesterday, after trying several things.
Firstly, I take my figures through the Quests involving PVP. Why? Because they also "tick off" Gold for upgrading from your list. You'll need to use your preferred method of Gold farming less if you first get Gold from PVP Quests. If you already have all Gold you need before this point, you're essentially making the Gold from the PVP matches go to waste.
Next, I'll do the Heroics in Giants. This will usually get my Skylander to a good level. Also, I like to do these before the SA Heroics because if you finish them all you will have max stats when doing those. After them, I'll finish the Quests on Giants. Why the heck not.
Naturally, after that I pop SA in, finish the five Heroics on that, then I cross-check on Giants to make sure all possible 45/50 Heroics and all do-able Quests *looks at

* are complete.
And of course, then I finish SF Quests. Elemental and Personal Quests vary, and I may do those first, but with universal Quests: I like using the first bonus mission with the Chompies until I get the Fruit Frontiersman Quest, as this will get you about a third of the way to finishing Badguy Basher at the same time. I use the Super Hungry Gobble Pods Survival Arena next, because that will level me a lot while going towards Badguy Basher.
I guess you can use the first Survival arena the entire time as that levels you better, but I just like using the first mission until FF is complete, as that's the easiest way I've found to collect fruits- and similar to the way I handle the PVP Gold issue, doing that later means the baddies you are killing in the mission aren't counting to anything.
(On a side note- you can do bonus mission related Quests after the PVP ones. That also gives you Gold, and again, it's going to waste after you're upgraded. It's just more natural for me, to finish the PVP Quests first, move to Giants and so on. But you could go from Giants PVP to do the rest of the stuff in SWAP Force. It won't make much impact. Since I have the Crane Deck exploit already set up for Giants, when I go back to Giants, I use that so I wouldn't need Gold afterwards anyway.)
Remaining levelling up is done in SF 3DS- the best levels to replay IMO are Shimmering Shard Shire and Bonsai Bay. They have the least intrusive cutscenes and neither of them have any lock puzzles. I also play the other levels from both of those worlds and the Sky Docks when I get bored of those, but that's just a personal thing.
Lastly I max out Gold. Totally optional. For Giants-compatabile character I use the Crane Deck exploit, then get as much Gold as possible from Woodburrow to get the last 535 I need to reach the SF max cap.
I usually use the Chompies bonus mission for SF characters- I get about 2k per run. Gold is abundant now though, so there are many methods you can use. I just like it more to naturally play with my characters. Screw exploits, this game is actually fun to replay unlike Giants.
BTW, just a warning for those of you who like to max out Gold: if you collect even 1 Gold in Giants when you have over 65000, you get reverted to plain old 65000 again. I tested this with my Series 1 Whirlwind. Thankfully, re-collecting the 535 Gold again is really easy by just playing through the hidden side-scrolling game in Woodburrow, or something.