Well any Skylander game that gives your toys a new adventure and exploration options is worth it .
Most fans here cheer the original skylanders for being less cartoony and a little more serious with a beautiful storyline and levels that are less random . Kaos is a bit more scary and intimidating i suppose .
It has a level 10 cap , only one difficulty setting and Heroic challenges which give stat boosts to your toy that supposedly carries over to swopforce but i never noticed anything .
Any of your new S2 or S3 toys that SSA recognised will work just fine on the SSA but no Wow pow no funny variant colour .I will be surprised if you only have a Spyro toy . I bet you have a few others you can use on SSA . Even if you dont well Swopforce has plenty reposes of some of the original toys still available and can be played in SSA .
In terms on monetary worth , if you find an SSA starter in a shop it should be on a massive clearance sale . If you are a skylander fan , i am sure you will enjoy SSA as much as Swopforce .
I read that you are a Spyro purist . Well with SSA you can customize your own pure Spyro Adventure . If You buy dragons peak adventure pack , you can explore a dragon kingdom level and get Sparx . There is also a Cynder and Dark Spyro toy to collect .
Spyro has always been about dragons and there are lots of skylander dragons to collect .