I'll try. Other people will probably add stuff.
Sure-Grip GT-50 are the equivalent "serious-roller-derby-beginner" skates to the Riedell R3. The difference between those 2 is mostly that Sure-Grips are generally better for people with normal to wide
feet and Riedells are generally better for people with normal to narrow
The whole package will get you through one to 2 years of Derby. Some of our girls still skate with their R3s after (what is it, by now...?) 2 and a half years, almost 3. Granted, their skates really need replacing now.
The nylon plate is basic, but the whole skates being made for the keen beginner by a serious Derby brand, you're safe.
Wheels: 62mm is standard. If they are the wheels I am thinking about, they are wide (more stable which is good for a beginner) and hard. Now, the hardness is always a big subject. Some people like hard wheels, some like soft wheels on one given floor. Then the floor itself can be more or less hard/soft. Then the weight of the person acts on the hardness/softness.
There are endless threads on skating forums, but if I want to keep this short: the floor we practice at in Bristol is fairly soft, so having a soft wheel on top of that makes it more sluggish and makes stuff like T-stops more difficult because it grips and doesn't slide as well. Having hard wheels makes rolling less effortless. BUT, it's a balance to find because a wheel that is too hard will not grip the floor in corners and will make you slide out and in the wall. So it's all about the grip Vs roll ratio.
Then, on top of that, the lighter you are, the less weigh you apply on the wheels, therefore you can afford having softer wheels than a heavier person. If you are heavy, you would want to consider going for harder wheels than a wee mosquito team-mate of yours.
The wheels I *think* you're getting with this Sure-Grip package are hard wheels. On a scale from 78-odd, which is soft, to 98-odd, which is hard, these wheels are 95.
I would say, put them on, skate with them, if you're sliding all over the place, you may want to consider buying softer (grippier) wheels. But before going grippy, try to lower your centre of gravity into a low Derby stance first!
Bearings: same as the plate, nothing to write home about, but it's fine to start with. On the ABEC scale, the higher the number (9, I think), the most roll (=speed).
I hope it helps, and I hope I didn't make any blatant mistakes. Someone is bound to correct me if I did.
EDIT: This is all assuming that you don't
have sh*t-tons of money to spare and that you are one of our successful new Fresh Meat skater and therefore will skate in Bristol with us!