What parts are necessary of upgrading in a Tokyo Marui Vsr-10 Gspec ?

[hemy]

Hi I have recently bought a Tokyo Marui Vsr-10 Gspec and it only shoots around 30m with the stock internals using 0.2g bbs. I am not satisfied with this range and I would like to at least get 50m+ out of it. I would like to know what parts are necessary of upgrading, what parts I could just leave stock and some recommendations. I have already purchase A King Arms piston, M150 spring and spring guide, however the air seal isn't as good with these parts as the stock parts.

Please can I just have general help because I am new to airsoft teching!
Thanks Rhys