The g-spot is such a personalized thing. It's hard to recommend something that'll work for you, like eri said. Personally, I like a lot of pressure on my g-spot so I like hard, curved toys, but that's me. You may be completely different.
I say, try some inexpensive dildos in different shapes to see what you like and then you can move up to more of a luxury vibe or something with more texture. Maybe try a glass toy like the Amethyst
by SSA glass and something more subtle like The Slender
by Doc Johnson. Just keep trying things until you discover what you love because it takes a while to really understand your g-spot fully.