Have a good look around the forums, I have only had AppGameKit for a short period and am using tier 1 with only having done a bit of C/C++ many years ago and then I wasn't very good at it.
However I found that when I had a go at tier 2 it wasn't too difficult to do.
As a test I took a tier 1 basic program in AppGameKit and cut and pasted it into visual C++ then changed the code line by line. I did get some of the syntax etc wrong but the forum community came to the rescue with sites to use for assistance and with the few mistakes I made.
Check out this post to see some code side by side in tier 1 and 2 and also help sites. You will notice the code is not too different.
Hope this helps a bit
Programming - AMOS on the AMIGA! / DBPro / Python / A bit of C C++ / now also AGK2! - Graphics - Deluxe Paint on the Amiga / Paintshop Pro / Photoshop / Lightroom / Grafx2
Previously worked for Prisma Software producing childrens educational software on the Amiga - Titles - Pepe's Garden - Paint Pot / Kids Academy range - Paint Pot II / Shopping Basket / Which Where What? / Blobs / Alvin's Puzzles