100% is the basic maximum. If you have racial masteries or weapon expertise as a class feature, then certain skills and spells can get above 100%. As for training. If you're still pretty new here, rank and have fun. Get to 50, learn what you can.
While it might be a bit harder to survive without mastered skills/spells vs. opponents with mastered skills/spells, it's certainly not crucial. If you would enjoy taking the time to stop and master a few things, then do so. Otherwise don't worry about it.
Another good strategy is to read the help files for your class skills, determine what you think are going to be your primary skills (or check out the essays section of the forum). When you reach a level where a new primary skill is available to you, stop somewhere around there and take some time to practice with it and see if you can't figure out how it works best for you.
Also, welcome to the game and to the forums. Hope you enjoy your stay.
edit: I should add that if you got "utterly worked", it's more than just the difference in mastered vs. unmastered skills. Equipment, and more importantly, experience with the game has alot to do with that. If you find yourself reaching a point where many people are repeatedly beating you. Shelf the character for awhile, roll up a new one, stay at lower levels (25-40) and learn the ropes before heading for 50. You will see benefits from training (and in certain cases can mean the difference between life and death), but don't let training get in the way of having fun and exploring.
Another option would be to start an adventurer, and spend time training and exploring to better learn the world. Then get out there and try your new knowledge. This will give you a chance to see how training can affect your survivability w/o having to worry about other players kicking you about.