Hm I'd like to write a piece thats melodic and kinda celtic or renaissance sounding any suggestions on what scales I should use?
I'm not sure really what you mean. John Petrucci's "Glasgow Kiss" comes to mind when I see celtic. That song is in E Mixolydian if it helps.
Gibson Les Paul Studio
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good suggestion but don't think its what i'm looking for i like petrucci but i'm not looking to do a neo classical shred style piece lol just an acoustic instrumental or something
Sus4 and Sus2 chords sound very celtic-y. A very easy way to get a celtic sound is to retune to DADGAD tuning and drone the bottom string while playing notes ontop of that. Infact, the drone is a particular element in celtic music that makes it seem like it is in that genre. Even in standard tuning, play the low E string without fretting it, and play overtop of it for a start. You probably won't wanna make a whole song that way, but it is a good place to start.

Not really a scale, but using the drone and the sus chords will go a long way.