You're definitely gonna want to use that 600w HPS for flowering. T5s are good for veg, but that light won't reach the flowers unless you grow a SOG.
You can build your own tent with black and white poly and 2x2s. It's really easy and it allows you to design where and how you want to. From size to openings. I can post some pics of mine if you want to see them, but you can just google DIY grow tents for ideas if you want.
This is your first grow? Didn't realize, I think you're doing better than I did with my first plants. Lol.