My first suspension frame was the sex swing people have mentioned. It is a great start for a beginner and can be taken down fairly quickly.
If you have the MONEY, buy a suspension frame. I happen to like:
Bonds of Steel Portable Suspension
with an over sized topper.
if you don’t have the MONEY and don’t understand engineering/construction, go with a playground based bracket solution. Topologist mentioned it earlier in his post:
If you have room for an A-frame design, these corners are affordable and make an ultra sturdy frame. Just add wood. Whole thing can be assembled for under $200 to any dimensions you choose.
If you understand the engineering, wood beam loading wood construction techniques, build a frame over designing it for static/dynamic load and force in any direction of movement. This means you need to know things like how to find good wood in a lumber yard, where holes should go and where cross members should be and how to attach them.
If I was in your shoes with a smooth ceiling, I would cut it open, put in a hard point. Alas, I don’t have smooth ceilings but these swirl pattern which I am in no mood to replicate before moving out.