it would be easier to grow a single strain in the tent - though I don't take my own suggestions, I'm growing 2 different varieties in my small tent, my first indoor grow. you would want 2 similar plants in grow patterns, at least for convenience.
genetics is important - maybe first decision is whether to go auto-flowering or photoperiod variety. i would suggest photoperiod, as I think its more forgiving for beginners like me. also, my plans always included cloning, which can be awkward with auto-flowers (i heard).
start with single tent, start with clones/seeds, go through vegetative phase and start the flowering phase. at that point, think about a second grow area/tent - when you can propogate/grow vegetative batch while the first batch matures to harvest. you can then rotate the vegetative batch into flowering, and start another vegetative batch to replace...etc.
bigger tent or not, that depends on your circumstances. i started with a small tent 2' (W) x 2" (L) x 6' (H), and just getting into flowering phase. i am preparing for the next batch - taking clones now - to replace this flowering batch in about 9 weeks time. i am considering buying a larger tent - making this first tent the vegetative and the second/larger tent the flowering chamber. But i already have a T5 flourescent setup for vegetative/clones. so, you will end up expanding - but start with a single tent, as large as you can.
start small, then expand - smaller operation is easier to manage. the first grow will take the longest, then hopefully you can expand and be more efficient. start small, keep it simple.