You have to be careful about the big box torch. You really need the smaller aircraft size ones, ideally. It wouldn't be wise to dump the cash into the sets designed for welding and cutting. My gas supplier doesn't refil or swap the little bottles and if he did it would be at the bigger bottle prices. But those deals vary. I have a friend in Oregon who has really low refill prices compared to me.
The biggest cost are the frame prep tools. The tubing used in bikes, particularly in newbie hands, distorts and needs the various contact points recut. Those tools cost a fortune, between 500 and 1000. So at the least you need to find a bro deal locally with another framebuilder or shop to cut those threads and surfaces.
You don't really need a jig. A lot of folks doing this hobby want to play at frame builder. They want to do things like the big boys do, maybe get into selling frames later, or at least play in the shop with the same toys. Very cool. But if all you wanted was to make a frame, then you could get by for a lot less. It takes some looking around though, because the main discusion is about the pro stuff this isn't the EAA, or ChopperHandbook, or the blacksmiths were everyone is trying to come up with the simplest way of getting there.
There are certain advantages to lugs. The downside is the cost, and you will probably need to practice somewhat first. The upside is that the parts help you with the copes, the tube positioning, and if you can get the parts in relationship to each other you can pin them which provides enough security to braze the lugs in a Park stand.
If you wanted to build a bike custom but didn't care about lugs, welding has some advantages, but jigs do start to become more of an issue.