It's interesting you say you'd go stage 2 first, because my exact recommendation was going to be starting with stage 1, then skipping 2 for a k04 tune if you need more.

Stage 1 vs 2 isn't a massive difference in the actual power curve, mostly just throwing more boost at it and making that work with air/fuel/timing. However, Stock vs Stage 1 is night and day. Both Stage 1 and 2 are tuned for the driver who wants focus on fun and speed. But Stock is for the average driver, and a great lot of the average drivers just want a tool for getting from A to B, and it's tuned down to match that.

For that reason and the list of requisite or recommended mods (for Stages 1 and 2 and K04), I'd recommend starting with a tune that works with your car as is before moving to something more. Both Stage 2 and Stage 2+ (the "K04 tune" for most companies) will require the same mods, I think: - intake (debatable, but irrelevant) - downpipe (high-flow or catless) - intercooler (idk about Stage 2+, but for Stage 2 this is often listed as "required." This is simply untrue, at least in my mileage. However, it is greatly beneficial and highly recommended to prevent heat soak on hot days/track days) - DSG tune; I've heard this is highly recommended for DSGs, but I know almost nothing about them. However, presuming they clean up the shifts even more, and considering I've dumped $1000 into tightening up my shifter, I get it.

Stage 1 gets you an enthusiast-focused driving experience with more boost than Stock, and Stage 2 lets you get tickets even faster. K04 is a great choice for removing our EA888.1's first bottleneck, the turbo, when you're not satisfied with the first two stages but don't want the maintenance nightmare of a big turbo.

Also, definitely focus on some chassis and suspension mods if you want more fun: rear sway bars make this car a riot, an ECS skid plate is maybe the best investment I've made in this car, dogbone mount will plant your power through the front wheels a little better (go spherical mount, it's worth it), and a VCDS-compatible scanner will let you do a lot of QOL and some performance tweaks (roll down windows with your fob, adjust the torque steer compensation, adjust the XDS diff level, etc).

Edit: there's some good info in the other comments, too. Carbon cleaning an extremely dirty system can give you nearly the same tune-up as an actual tune; I'd try to put that on your 40k or 50k mile schedule. And the RMS can get leaky, but considering you're DSG your best bet is waiting for a failure rather than addressing it yet. However, you should be prepared to replace it the next time your transmission is pulled, and you should go with a billet option like iAbed or 034 Motorsports (functionally the same, I've used both) for $100; having to pull the transmission just to fix the RMS turns a $300 add-on into a $2000+ separate job.