the most common thing that pvp people do is use save editors (in all fairness though not everybody uses these, many people play through the game a few times then decide they want more of a challenge) to get say 99 souls of a great hero, this lets them level up fast and doesn't interfere with the way other people want to play. They aren't nodding any of there stats, its just as if they farmed souls for a very long time without actually wasting all that time. The same goes for common pvp items such as green blossom. Its not cheap and you can either farm it or buy it in the dlc. So they use a save editor removing the hassle. Most of the time all of these mods cause no harm whatsoever, it just makes the journey a little easier. They tend to be specific pvp builds and will have gotten to a certain stage in the game to have decent weapons and magic.
regarding a good build for pvp id suggest sticking to a certain weight limit that you are used to. If you normally fast roll then make sure your build can accomodate that. There is no point changing the way you play best because someone says its better that way. You may want to look into buffs such as crystal magic weapon or pine resins, other alternatives are sunlight blade and dsrkmoon blade. The weapons you choose should fit your playstyle. For example if you are good with heavy hitting poise demolishing ultra greatswords then use those alternatively if you prefer rapid attacking rapiers then by all means choose those. It depends entirely on what you are most comfortable with. Every now and then you may want to switch it up a bit and if so then do it as you might discover that you are better at fighting in that way rather than the other.
whatever you chose to do enjoy pvp and enjoy dark souls
the last thing i will say is to just jump in. No amount of research can prepare you for the experience of fighting another living human. You can look up stuff as much as you want but the real deal is the best experience there is.