Everyone is different, so work out what works for you then stick to it. Some people have a high tolerance, others have a low tolerance.
TrueStart is a reliably caffeinated coffee that allows you to boost your body and mind by taking control of your caffeine intake.
The EFSA recommend a maximum daily allowance of 400mg (200mg for pregnant or breastfeeding women). For sports performance, 2-3mg per kilogram of body weight is most widely accepted optimal level, according to a number of research papers.