Since I haven't seen anything here posted about it, there was a bit of a debate a week or so ago on what the PVP SL cap would be, either SL120 or SL150. It was decided that SL150 would be best for PVP as it gives you plenty of viable builds without a "best" build emerging.
The Bandit is the best starting class if you want to build a melee character as you start with the absolute lowest attunement and intelligence, which are rarely needed for melee builds.
The Old Mundane Stone can be infused with a weapon to make a mundane weapon. This means that the weapon gets ridiculous scaling off of your lowest stat. It works by taking your weapon's base damage, halving it, then adding the mundane scaling. Mundane scaling gives you 80 damage when your lowest stat is 5, increasing by +6 each level up to 20, then +3 up to 30. In a practical PVP sense, you can get SL150 with 22 across the board giving you +176 damage to your mundane weapon. Depending on what weapon you use, this can be a huge improvement to damage. Mundane builds seem to be pretty decent as they give you a lot of versatility without sacrificing too much damage. They also seem to work very well with some hex related things.
I haven't played as much as other people (or even beat NG), but I have done quite a bit of PVP and tend to win more often than I lose, so I want to share some tips. While builds can definitely give you an advantage, playerskill Annoying Oranges numbers. As Dark Souls players, I thought we'd all know this by now (seeing how many bosses seem to 1-shot us a frustratingly large amount of times), but many people seem to ignore that, so use that to your advantage. Stamina usage is key, NEVER USE ALL YOUR STAMINA. There are so many times where I threw away my advantage because I used my last bit of stamina to swing and miss, leaving me open to a counterattack. Keeping that bit of stamina up gives you that option to roll which so often saves us from certain death. Also, try and stay below 70% weight, fat rolling gets you killed.
