Never really asked for help on the forums before so here it goes!

I'm self taught and been playing for about 2 years, I did grade 8 piano but now I want to take some grades on electric to discipline me. I'd quite like a certificate for all my hard work too!

I know all my scales, (Major, minor, dorian, phrygian etc...) at semiquavers 110bpm. My arpeggios are getting there but not all the positions, and I can solo in blues pretty fluidly.

So far the songs I have learnt which I'm most impressed with are probably Tamacun, Hanuman, Ixtapa, by Rodrigo y Gabriela, I like playing Jazz as well, and my technique has improved a lot lately.

Can someone give me some advice of key things to learn for grades and what grade they reckon I should try for? How difficult would it be to jump in at grade 8?
Judging by where you sound in relation to me i'm pretty sure i would need to start at Kindergarten.
You're going with RGT, right?

It's very hard to tell just from a lump of text. Grade 8 after two years would be crazy, but with a background in music I guess you know what you're doing. Although knowing all the theory is one thing, knowing all the technique after two years and knowing it at grade 8 is a stretch.

Have you got the syllabus books? They cost like £10 each and will guide you in what you need to know. Maybe go see a teacher who teaches RGT and get them to assess you?
Thanks maybe I should buy the syllabus book! Are there any techniques in particular you find in graded exams I should know about?
Strumming. That's one.

I have no idea what to suggest to you because I don't know what your ability is. You need to be able to play clean, can you go see a teacher?

In the Guitar Techniques forum there's a sticky where you can post a video of your playing and the teachers will assess you. Post it there and they'll give you some advice.