Be kind to future yourself so that you may give yourself a pat on the back and a warm smile because you made a good decision.
Learn C++, Java or HTML5.
Additionally a little bit of relational database stuff; even if it is for a hobby, make it a good hobby
The age old programming languages are here to stay for decades; you will not regret it in say 10 - 15 years time when the unthinkable may happen. The just being in C++ community, the Java community or the HTML5 community opens the door for a lifetime of principles which can be applied to more than just programming.
These are more difficult to learn, but more rewarding to you and the people around you. Sometimes people say that something is difficult, but you may not be among such people. Give it a try, it will not kill you.
If you struggle to enjoy learning HTML5, C++ or Java, try C#, Visual Basic or what ever language Unity3D uses or an equivalent; anything with a good track record and consistent updates.
As for AppGameKit or DarkBASIC in general, use them anyway
; it will compliment your learning, but as NonZero stated; limiting yourself to ONLY AppGameKit or ONLY DarkBASIC will teach you many bad habits that C++/Java/C#/VB.Net would have prevented you from being stuck with
As for AppGameKit vs DarkBASIC
, these are incomparable products for completely different markets; do not compare a multiplatform model to a single platform one; each have their advantages.
These days multiplatform is a buzz word that attracts and impresses people; but multiplatform will sometimes mean less features and more workarounds. If one cannot get ones products to work on more than one platform, then there was no point in using the multi-platform tool in the first place.
How good these tools are falls down to the skill of the programmer. However, neither are bad or obsolete.
I'd pick AppGameKit, even though I do not use it; I use DarkBASIC Professional for something specific
which AppGameKit could not do for me personally, not because it is better than AGK. Again, two different tool-sets for two different markets.