I want to get my 2015 vw golf gti to 300hp. what is a good solid way of doing so? What route would you take?

Throw enough money at it and anything is possible.

From Google.

"Compared to the GTI’s powerplant, the Golf R’s engine has a modified cylinder head, exhaust valves, valve seats and springs, pistons, injection valves and larger intercooler and turbocharger. DSG equipped models also come with an auxiliary oil cooler on the passenger side."

As well as the the R model is equipped with AWD / traction control system, which lets you actually use the HP. 300 hp in a light FWD car starts to get impractical, and downright scary to drive.

Lastly, mods like that will invalidate your warranty, probably cancel your insurance AND probably drop $10K OFF the value of the car.

Seriously, go and trade in on the R if that's what you want. It should actually hold it's resale value better over time (being a limited production run, and having a bit of a cult status.

Just get a tune. go on the websites for APR, UNITRONIC, or a reputable tuner. They hook up a laptop to the cars computer (ECU) and load their software, or you might have to take out the ECU,and send it then get it back in like 2 days. This mod just changes the cars fuel,timing,boost,etc. .settings and lets you see the potential the car has from the factory. You wont need a aftermartket turbo, possibly just a 3in downpipe.

Trade it in on a Golf R.292 hp,all wheel drive and superior suspension.

Full exhaust full intake bigger inter cooler and a serious tune and that's it should hit 300 no problem maybe a boost controller

Wave bye bye to your VW vehicle warranty!

You can kiss your powertrain warranty goodbye if you do this - so don't . it's fast enough.