Leave plenty of space for your indeterminate tomatoes.
Indeterminate varieties will spread out all over the place and keep producing as they spread. Determinate varieties are only worthwhile if you are machine-picking or machine planting or something.
I did not stake or Trellis my Sweet Millions. I simply put some straw under them to keep them off the ground, or let them rest right on the perrenial clover variety (I think it was Dutch White Clover) that I had growing around the tomato plants as a ground cover. There was very little loss of fruits to ground-contact-caused rot. Nor did I find pruning worth the effort. I found that the new vines produced about as well as the earliest vines, so I saw no need to prune. I could never figure out any of the pruning systems that I read about, any way. Yea, I pruned off dead stuff and stuff that I couldn't keep off the ground and started to rot, but that's it. When I first started growing tomatoes I followed all the recommendations about pruning and staking or trellising but I think it was a waste of time. You might want to allow MORE space per plant than package instructions say. 2.5 square feet per plant, not the 2 square feet that is usually recommended. This seems to produce a better yield pr square foot.