Fillet brazing isn't intended to be light
"Going lugless" isn't typically done for weight savings, and the poster who suggested fillet over TIG is correct - fillet is easier to learn to do at a basic level (note that I'm not saying that *mastering* the skill is any easier), cheaper, and far more forgiving of mistakes. I've helped friends learn to safely join tubes with fillet on the O/A setup in a single afternoon. That's not saying that they're ready to run out and braze up an S3 tubeset, but with basic, thick cromoly tubes, and some patience and care, a beginner can do a safe (if not all that pretty) job of building a bike.
Get an O/A setup, get a bunch of scrap tubing, and braze up some fillets. Then try to break things, cut up the joints to look at where the brass went and where it didn't, etc. When you think you're ready, build a bike. Forget TIG unless you want to become a professional builder - it costs a ton, it's hard to learn, and the only advantage, really, is speed, which isn't a concern if you just want to build one or two bikes.
-Walt