3D print your own DJI Mavic Pro
This is kind of silly, but I guess if you wanted to go the budget route and make your own drone but not spend any R&D money into building one, you could just copy an existing drone like the Mavic Pro and 3D print it. Sure, you don't get the flying precision or the tech, but if you just want something that looks like the Mavic Pro that also lifts off the ground, I guess this is your cheapest option!