EN1

Id highly recommend the Flexispot EN1. Its around $200 or less (depending on the size), and is probably one of the most popular budget options right now. You can find some good options in this thread

Flexispot en1 on Amazon, I ended up sawing mine but you may find a size that you like

So...I just bought the following from Amazon. I've had it for a few weeks and it seems good. I can't speak to it's longevity though. Walking Pad with Incline, Under Desk Treadmill for Home, 2.5 HP Portable Treadmills with Incline, Compact Treadmill Small Running Pad with LED Display, Remote Control

for a smaller room, I'd take a look at the Flexispot en1, it comes in plenty of sizes

I was in a similar situation although I was leaning more towards either getting one of the E6 models on Amazon when there was a small discount code during the Prime Days sales or the E5-Lite (which I believe are very similar to each other). But I was also looking at the cheaper EN1/EN2 models. I def

It is the FlexiSpot EN1 55 x 28 inch desk with adjustable height. They offer different sizes and such. If I had the space I would go bigger myself.

the flexispot en1 is a good budget option, you can get one for $100-$200 right now depending on the size. You can find some good options in this thread