I started with Paint.NET, which is some basic (and most importantly: free) graphics software, but at some point I realized I'll need something more complex and partially switched to Photoshop. So, basically I'm using both programs, PS offers a great diversity of effects and allows you to work with masks while Paint.NET is much easier to work on when it comes down to moving/transforming objects throughout the layers, especially when you're working a lot with transparent backgrounds. Also, Paint.NET has more usable text tools.