There's no point adding power without improving control, if you can justify and afford the cost, go for it.
LSD is a big ticket item, not experienced one in a Mk5, but the one I do have it's a huge improvement over open diff, shocking how much extra drive it gives.
But fitted it is as much as really decent suspension set up that you are planning to do anyway
I would go for suspension first and see how you feel after that.
Brakes also can be improved too - Mk7 R calipers are a great bolt on upgrade
Also consider bushes - yours is low milage, but its likely some bushes are worn or even seized - maybe visit your aligners first for a suspension health check before doing anything.