How to know the rings measure that I need?

Hello, it seems to me that when you do a job of these you must think of a budget factor, since if you want a very durable result, you will get a little more expensive than if you decide for something simpler, I would think that since you are self -taught you should start with something simple as a ring and a change of caps or a partial, change of valve stamps with sitting of them, retenes, carburetor adjustment. I exosto and ready, it is also only when you evaluate the compounds that will be the change or reuse of the Ring, you know that with a workshop and ina galga handle, if so you should change piston, of the caps, if the Sigual shows 2 types of diameters in the rolling of the cap (only if it is reached to perceive), it will be the rectified, otherwise you can change the caps of the same measure, that if it changes all the seals that you find, the valves you find in some cases and only the valves I reuse guides and seats, practices an assentamineto, keep in mind not to disorder them after sitting and practicing good cleaning to the cylinder head.
I hope I have given you autumn point of view

Thank you very much Jorge_zrate, in reference to the budget there are no problems, what is being complicated is to find the new pieces or spare parts. I am from Mexico and I still can't find the rings.
In addition to many technisisms, words or concepts that I still do not understand at all.
But thank you very much for your contributions, advice and comments, that is appreciated
greetings and good vibes !!!