Cedar is probably your most accessible option for woods resistant to rot, but it doesn't really matter as long as you pay attention to it and slap on a fresh coat of poly (or whatever you end up using) every once in a while. pine construction dimensional lumber is probably going to be the cheapest option.

Big thing is probably the feet, you don't want them resting directly on the ground or even cement if you live in a wet area. It'll make it a lot harder for water to seep into the wood and rot it. It's not really wet that damages wood but prolonged wet. Getting rained on occasionally won't do much for a long time, but sitting on dirt wicking up water day in and day out will rot the leg in a year.

A good base to start with is a "2x4 workbench" -- a very (very very excessively very) strong workbench that can be made using just 2x4s, a circular saw, and a drill. They're very simple to make with zero experience and minimal tools. They're also incredibly heavy so you pretty much want to build them in place.

Just google "2x4 workbench" and you'll find plenty of different examples and sets of instructions.

Should be pretty easy to modify to be the kind of three-tiered potting table you want.

You'll also need to seal whatever you make to protect it from the weather, if it's going to be outside.

If you don't have coax in your walls already then you want to hire a professional. It's possible to do it yourself but it's going to be a huge pain in the ass and a ton of work. The professionals already have good specialized tools and experience to get it done in a fraction of the time.

If you just need to terminate the coax coming out of the ground and there's already a junction box with a bunch of unterminated coax that's running to various rooms in your house, then get a coax termination kit, something like this: https://www.amazon.com/Coax-Crimper-Compression-Stripper-Connectors/dp/B06W5G64VQ/ It may seem like a waste of money to buy a set of tools you'll only ever use once. You can get a stripping tool, compression tool, and a bunch of connectors for $20. If there's multiple coax cables in the termination box you'll get the clearest and cleanest signal without using a splitter, so you might want to get a tone-tester as well so you can easily locate the cable which corresponds with the outlet you want to use.

You can get a little baggie of twist-on connectors for $6 and strip with a knife. Don't. Get the kit with the proper tools. The extra $14 is totally worth it.