Synthelamin (inj B-12) increases red blood count. Which in turn, you get more energy, more vascularity, a greater overall 'feel good' feeling and what most people use it for - it increases your appetite like mad.
Better for what you are asking, try a combo of Syntheselen and Synthetine together -
www.synthetek.com Great combo for a 'little kick before a game'. But it will not make you jittery, anxious, etc. You have to inject them both IM.
Are you drug tested? If so, you can't use Syntheselen as it contains Heptaminol which is on the IOC banned list
Clenbuterol is defintely not good for you, as it will make you feel like crap - shakes, anxiety, etc.