If you're just new to gunpla this question might have popped in your head: What gunpla grade should I buy?
Since I've been building quite a lot of gunpla maybe I can help you out answer this question. Let me go through each grade that I know of.
Advance Grade (AG)
This grade is actually the simplest 1/144 Bandai has to offer. It's a kit well fit for young ones due to the easiness of the build and it's limited movement (only head and arms move). You don't actually need tools to build this. This is definitely not a good kit to start with if you want to know the basics of gunpla.