I started with modul8 wich is great as a pure video mixing tool, as it has a very nice dynamic interface that allows for some funky video composing (it uses the same kind of “fake 3D” that after effects does (like video on planes or other primitives in 3d space, but not real 3d).
It starts to feel a bit limited after a time, but for what it does I hold it as the best one (compared to resolume/vdmx etc.) as the interface is great for playing and allows you to to quite a lot with simple footage.
The external harddrive where I kept all the video photage broke once when I was VJing at a 3 day music festival so I ended up doing several sets using just a square & a circle I made in photoshop + whatever photos I had on the desktop. worked pretty good actually
I still use it for doing the things it can do (like straight video mixing with sound reactivity and so), but generally I use max/jitter as it lets you do pretty much whatever you want, and incorperates 3D pretty nicely.
It doesnt allow you to model and so (unless you type out the 3d vecors), but supports preanimated models and is super for sound reactivity, especially as I also use it for things like granular synthesis and it is a very friendly software in terms of recycling parametres.
(I have a real-time patchable sound reactive 3d model mixer I build it max if anyone is interested, its pretty funny/funky as you can map sound characteristics like volume/peak/brightness/noisyness/rise/fall/tone etc. to stuff like x/y/z rotation/position/color/light etc.)
Its not free though (max I mean, the 3d mixer you can have for free if you want it )
For a free software that handles realtime 3d I’d go for unity or unreal.
(the unreal render engine is a lot better, but can be a bit of a headache for ppl who dont like interfaces/are familiar with 3d software, unity has a not very beutiful but fully capable render engine and a terrible interface, but it lets you script/write/rebuild whatever you want (however you want) including the render engine, so its definitively acceptable as an option.