For equipment in PvM leveling you can check out the pinned guide here on the thief class forum.
You can reset your skills for free by talking to the mesmerist in pront(near the quest boards) but for the stat reset you need to buy reset stones or acquire them as a reward for finishing a set of quests.
As for PvP SC, in my oponion there are 3 builds:
1.) Pure Masq/ Debuffer a.k.a WoE build - Kills in PvP using Manhole and Traps. This type of build has max Dex and Int to achieve "no cast".
2.) Tri-shot/ Bow build- Has high dex and agi to ensure high damage out put from bows. For this build, high agi is needed for Triangle Shot. Also works well with the ff skills: Severe Rainstorm, Arrow Storm and Aimed Bolt. You can check the screen shot thread for samples.
3.) Str/sword or dagger build- Has high str and dex. Str for high damage using swords/dagger, high dex for masquerade/divest and moderate agi for sleep immunity and atkspd. This build might not be as good as a debuffer compared to the previous builds above but it can work. Skills used: Cross Impact, Ignition Break, Bowling Bash and Backstab(yes Backstab).
I'm currently working on the str build for now.
Edited by Usurper, 22 October 2016 - 10:52 AM.