WOOO! Which route should I do first?

Pacifist

Good idea

It’s perfect for new players!

geno =)

Hell yeah

I reccumend playing natural first.

Gets you into the feel, yk?

I'm not gonna suggest you do one first, but I know that
1- genocide is heartbreaking
2- True pacifist is extremely difficult
3- there's neutral which has an amazing final boss but unless you're doing genocide you'll get that one anyway
4- pick one ending and stick with it. If not either you'll have to go through the whole game knowing you messed up your ending or restart it prematurely and have Flowey eternally guilt you