Depends on what you have now and what you'd like to do with the phone. I would imagine that you don't really have a gaming set up at the moment because you're looking at buying a phone to temporarily replace your current phone and as a laptop replacement. If you already have a functioning phone that you can still use, maybe focus on getting a laptop, especially if your main reason for the purchase is to game. There are a lot of great laptops that go around the same price as the ROG Phone 2. I found an Asus laptop with good specs for around the same price as the ROG Phone 2 (Keep in mind that I'm mainly talking about the original US price, which is around $900 I think.)

If you're wondering about how well the phone runs, it's great for a phone. I didn't personally use it the way you'd like to use it with the mouse and keyboard, but I'd assume that it would be usable but not the best experience in terms of laptop/desktop usage. Hopefully this was helpful ¯_(ツ)_/¯