Honestly, I would say buy a used bike. You will get way more bike than you will for a new bike. However, if you are worried I understand buying new because of fit etc.

Don't let a shop put you on an oversized bike. I would stick to flat pedals until your riding is at a point where clipless makes sense.

YOu can get a really nice bike for a beginner for 700. You can also try something like a bikes direct motobecane. Its usually cheaper for similar components as a "name brand" bike like specialized etc. Thats what I did when I got more into XC (i use to dirtjump and BMX etc). Spent $999. I wanted a 4130 hardtail frame, so I was specific in what I was looking for and they had a chrome 4130 29er. The components were good enough and I rode it stock. Over time the only thing I still have left is the frame, everything else has been upgraded. The bike I have now would be closer to $2000. went from the loose ball hubs with WTB rims to Hopes with Stans, went from the Rockshox fork to an X-Fusion Air fork etc.

MTB... everything pretty much has a premium price for no real reason. It's just how it goes. A lot of stuff the differences form midrange to high end is negligible for most riders. Like cranksets, for example. SO yea... don't buy a Walmart bike. But a newbie on a $600-1000 bike is plenty content. There is zero reason, imo, for a newbie to spend $2500 on a bike. There is barely reasons for an experienced rider to spend that much. To me, at that point you probably know what you like and are better of building a custom bike or upgrading. Thats just my opinion, but like I said, I come from BMX where the idea of buying a "complete" bike.... no one serious does that. You build from the frame up. In MTB a lot of people tend to upgrade their midrange bike as needed. Personally, I find riding a custom to be more fun and more personalized.