How should I use my extra closet room? is a 2.5Gal...

Once you get good enough with being able to know what your plant wants and provide it with plenty of light you should be able to yeild about a lb per 5 gallon pot. So I would say it is doable but you would have to train the hell out of it and provide it with enough light and nutrients perfectly with no dificiencies. I have personally been using the viparspectra and highly recommend them. You just can’t beat the quality you get for the price. I would recommend that if you are going for a bigger harvest to get the more powerful light however. Hope this helps and good luck with your grow!