1st Closet Grow - Supply and Setup -Help please :)

Hey everyone this is my first post and I want to remain somewhat discreet but I will give as many details as possible.

First, closet grow space, I believe the closet is about 5x6x3. There is no door on the closet at the moment so I'm not sure what the best type of door i should put on it. Now I understand the cycles fairly well but I need help learning how the ventilation system works.

Setting up I will have a 400W HPS light with ballast. (Can I grow the seedlings under this or should I grow the seedlings under say a desk lamp? So far I'm going to run down the supply list.

1. 400W HPS light with ballast
2. Soil (Organic and then mix with 50/50 Perlite mixture)
3. Grow solution (Foxfarms if I can afford it)
4. Bloom solution (Foxfarms if I can afford it)
5. Vitamin solution (Which is best?)
6. 3 or 5 gallon grow pots? (What type is best?)
7. Starter soil for seedlings
8. Small fan on 24/7?
9. I don't fully understand ventilation systems but do I need to use piping on the bottom of my door to help the airflow?
10. Either white paint for the walls or Mylar?
11. Bubblegum seeds (10)
12. On the bottom of my closet what should I coat the floor with?
13. Temperature and PH monitors
14. Timer for Lamps
15. Extension cords electrical outlets etc.

For germinating I heard paper towels are not the best so I was thinking about doing the cigar casing thing with a little bit of water in the bottom, does this method work? Should I cover the cigar casing or just leave it open? Does the casing need light?
I also need to decide on what type of "door" I need to use for the closet I was thinking Of getting just plywood and then cutting holes in the bottom to put the piping for ventilation? The high quality equipment is that more for more effective growing or just growing period? Like I hear Mylar is the most efficient but is painting the walls white just as good for cost cutting. What do I need and what can I live without? I'm looking at a budget of around $500 so quality is a factor but cost-cutting would also be relative to my situation. I'm hoping for a yield of 100g+ so I'm looking at planting 4 plants then sexing them and hoping I'm left with 2-3 plants just wondering what kind of yield I should expect.

Sorry I wrote a lot and asked a lot of questions but any type of help would be great :) Thanks in advance, Happy smoking :jointsmile:

you can grow seedlings under hid lighting but it needs to be atleast 1-1.5' away from the tops of seedling.

on ventilation look at diy airvents, or you can use pvc piping. you dont want any light leaks period.

pot size depends on how long you veg for or how long they grow for. you want about 1 gallon of soil per foot of plant

mylar is expensive and gets dirty fairly quickly. flat white paint is great and cheap to work with

on the floor of your closet i would put some heavy plastic(painters plastic)

temps should stay around 70-80 is optimal

good luck and read