For full body I would go as big as you can to make sure you get even light from top to bottom I’ve got a 60” Profoto umbrella that I think is a great size. If you’re looking to save a couple $$ westcott has some good umbrellas too. Another thing to maybe consider is to use a v-flat with a light bounced into it. That always creates nice soft light too. Heres a video inshot a few years back where I use a v-flat for a full body shot.
For full body I would go as big as you can to make sure you get even light from top to bottom I’ve got a 60” Profoto umbrella that I think is a great size. If you’re looking to save a couple $$ westcott has some good umbrellas too. Another thing to maybe consider is to use a v-flat with a light bounced into it. That always creates nice soft light too. Heres a video inshot a few years back where I use a v-flat for a full body shot.