if you cant feel them when you touch them, you might have damaged nerves in your arm from shooting up..
Tramadol blows - it is known to cause seizures :S Try to find some stronger narcos like hydrocodone, vicodin, etc. They are more potent and aren't as dangerous to abuse compared to tramadol. Just be careful, opiates are habit-forming and can harm your liver.
its a thin line, by the time you take enough to get a buzz, you are going to be sick, it's a crappy med, I used to get 100's of them for dirt cheap for just that reason, no one wanted them.
Depends what mg it is. I would take no less than 1 gram. Meaning you need 40 25 mg's... Or 20 50 mg pills. Or even 10 100mg pills. Parachute them, yummy.