I wouldn't actually recommend T3 to a beginner and not to someone who has not been dieting and working out consistently for the last months or even year. T3 is a great compound to lose the last little digits of fat among those who want to compete. Before you actually use it, I would recommend checking your natural T3/T4 levels. If you do use it, you should be aware that it can suppress your T3 levels just like steroids suppress Testosterone and there's no PCT for it, except for natural compounds for T3 PCT, but as you can guess, they are not as effective. So you have to go for the slow withdrawal method. moreover, to avoid permanent damage/too much suppression of natural T3, you should not use it for longer than 8 weeks.
dosage-wise - it starts at about 25 mcg/day and can go up to 50-75-100 mcg/day or even 125 mcg/day for a man. then slowly back down (withdraw). but again, i wouldn't recommend it.