Tamp will not overcome dosing or grind inconsistency. My experience indicates tamp is rarely the issue. Amazon sells several several scales that will do the trick. Forget tamp until all other issues are resolved. Matt Berger has a good post about tamp on his site, which I agree with.

Always good advice here. Inconsistency as a newbie with new equipment is all part of the experience. Stick with it and adjust variables one at a time. Eventually it will all come together. That's part of the fascination of espresso. It wouldn't be as rewarding if it was easy.