There's different options you want to do soil or hydro first, do you need a grow tent or want to build one or do you have a closet that's its going in.
I would say either put panda plastic or paint the walls white and what are the dimensions cause you should have I believe about 50w a square foot. How tall do you want the plants to be. My grow room is 3 x4 and 4 feet tall I have a small 6in fan on low with a 400w hps I am flowering 2 bushy plants good I could fit 4 under it though. You would probably be better off with 600w hps/mh.
White reflects the light back but doesn't create heat spots to burn the plants. I added more to the other post too.
You can do a lot with a room that big. If it was me I would section the room of into two rooms one for veg and clone the other for flower.
So many defferent lights and set ups out there so I can only tell u what I would do if it's me with that space. With that said. I would put two 600w metal hailide/ high pressure sodium with cool tubes. Th reason for two 600w vs one 1000w Is two 600s are for efficient than one 1000w and you can get more coverage with the two.
What would b a easy strain to start with how to u run the power generator or just plug it into the wall?
The strains are endless for beginners. But since it's ur first grow I wouldnt dish out a lot of money for seeds because u will run into some issues and u dont want to waste mony on some seeds.You been smoking awhile so you might have some bag seeds laying around that's what I used on my first grow. I started with 12 seeds 8 were fem but by the time igot to harvest I had one lonely plant. With the gen im not to sure what ur asking
Just plug it strait into the wall but I have it plugged into two deffernt outlets ( deffernt brakers). You just can't run more power through a breaker then it can handle.
You should run the lights through a surge protector at least that's what I do. And the two room thing would be really good I have a veg tent and flower tent. You could divide the room using the panda plastic or anything similar. For lighting I run fluorescent in the veg tent and hps in the flower I do it to keep the electricity cost low. I also veg one week under the hps before flower.