Considering that I stopped playing for 6 years and then came back, I may as well be a new player, so I believe I have at least some knowledge to give.
1. Focus on your character - a lot of lower levels want a mount for naked hunting to get money and staying at that level for valour. This isn't a bad idea, but it also slows you down. There is a set amount of valour you can get at lower levels and the amount of silver/copper dropped per monster is low, when in the same amount of time at a higher level, you can get way more per fight.
2. Learn to love crystals of truth - back when I was first playing, these things didn't exist. In addition to the first point, they can give you a permanent boost to your attributes through talents. While this isn't as much of a big deal when you are level 15 or something, they can make a huge difference in the lower levels.
3. Tablets and seals are your friend - following on from the above two points, focus on getting tablets for your character and later on when you get one, your shadow. These things cost quite a bit, but once again, they give you a permanent boost to your character.
4. Get a solid mount - after you've gotten your character to a decent point, in other words, maxed out on tablets and talents (or as much as you can be bothered) focus on getting a nice mount. The easiest one to go for are the city rep mounts (tigers or zorbs), but the chaos fighter mounts only require a rep of 3000 and become a very viable option at the mid range levels 6-8. It is hard to kill all those gungls and equally hard to feed jakarals, given they rely on you having a steady supply of chaos particles, but they are true beasts in PvP fights.
5. Valour - valour is only important if you don't want to fork out gold (or for bragging rights). The very minor difference between valour based purple armour and non-valour based purple armour is negligible and if you followed points 1-3, it won't make much of an impact.
6. Get a solid group of friends/clan - eventually, you will need resources outside your profession or other services, so it helps to have a group of people you can trade favours for and helps speed up waiting times for things, such as getting a certain resource or being healed.
7. Reputations - not as big of an issue at lower levels, but around the mid-level range, you will really want Great Dragon rep and God/Goddess rep, as they can tilt any fight, PvP or otherwise, into your favour.
8. Pets - lastly, look into getting a pet. Pet food drops fairly often, to the point that if you don't use your pet for every fight and save it for PvP, or rainbow/vertisda's rage runs, you will likely never need to buy any. They are a nice feature, which, if trained up after a while, can serve as a nifty boost in fights.