If you've got the room for it you can get an inexpensive press from Harbor Freight, you'll still need to fabricate some of the tooling to hold the parts while you press the barrel in and out of the trunnion and the barrel pin as well. I built my first one without a press, but it was a shitload of extra time and far more chances to screw something up. If you've got a place to locate one buy a press from HF and then sell it later if you don't need it anymore.
IMO screw builds are far easier, but you'll need the right screws and both a regular starting tap and a bottom tap. A drill press makes it much easier but probably isn't necessary. I used red loctite on the treads of mine and epoxy on the base and they haven't budged. Rivets take some specialized skills to set properly and you have to have the correct rivets and tools to set them or they won't be tight or won't stay tight long. From what I've heard screw builds detract from resale value, but since I haven't sold any of mine I can't comment on that.
If you're going to rivet you'll need to find the correct rivets and tooling. If you're going to screw build you'll need a drill press, taps and the correct screws. Save yourself a bunch of time and effort and just buy a complete receiver, unless you plan on making more than one you'll spend more money on the tools and equipment to make an 80% receiver than you will on a finished one. With a 100% receiver you won't need the bending jig or a spot welder. You'll still have to drill the rivet or screw holes since they don't come predrilled.
You need to think before every step. I've seen people drill into the barrel (all the way through into the chamber) and I've had to weld up receivers for people who couldn't locate the holes properly. And you need to make sure the rifle is legal when your done, meaning it's got the correct amount of US made compliance parts.
This isn't like assembling an AR from parts, there are a lot more tool/fabrication skills needed. If you don't have the skills to do this right you might want to practice on something less expensive.