Buy Counstruct2.
With C2 you can create all the games you want and keep the license for a lifetime and IF you want to port projects to C3 you can. If you're a slow learner like me C2 is better since you get to learn at your own pace and master the event system BEFORE you decide to buy C3.
C3 on the other hand, with its subscription license, you're obligated to learn everything there is about it and build as many games as you can within a year otherwise, you'd have wasted $$$.