I wouldn't bother with quests much until you get to higher levels 60+.
Buy premium if you don't have it already + pet + exp scrolls.
Get at least +20 FOC Khrentium armor (lvl 35) enchant with defense, +30 giant sword (change those every time you can lvl 25, 30, 35, 40, 45, 50, 55 etc.), ordinary reinforced physical dmg jewels +20 or supernus +15 enchant with crit % but it won't really matter until higher lvl.
Grind in Ancient Temple, Paraness SOLO, don't party with noobs. Stay there to level ~50.
Get at least +15 supernus FOC armor at lvl 55 enchant with defense, and get supernus +30 lvl 55 giant sword and can use it until lvl 65 or make lvl 60 exi one but too much work.
Then you can do Premium Dungeon runs in Triffi, South Hammerine or do some quests if you are bored.
Once you get to 65 get another FOC armor and reinforce as high as possible +10 is easy, with forge event +15/16. Get lvl 65 dungeon giant sword or theme battle sword if you want to do some pvp. You can make reinforced exi jewels too as they give 2x stat per stage.
When you get this shiz grind solo or duo in Wrecked Ship in South Hammerine until lvl 70 or something like that, save quests for exp events.
In raids all they need you for is dmg and hp buff so max those and their dna, buy extra dna points.
When you are 65-69 and have somewhat decent items I suggest you do some FOC (pvp) and learn your character bit more.
Here is lvl 69 build http://requiem-info.ru/calculator/14 you can use it for lvling and doing some pvp. Once you level over 70 you can reset your skills.
Warlord shines at end game but be prepared to spend a lot of money if you want to be good.
By that time you should know your class but here is a base skill build for lvl 90 http://requiem-info.ru/calculator/14 DNA is up to your preference apart from maxing your 2 party buffs and potens dash.