Kinda new player!

[MistakeNot]

Thank you all for some many helpful posts!

Besides equipped gear non is 100% spiritbound. So I can't convert it, right? About GC seals, someone told duty finder is best for that, I should just queue for "duty roulette". But I only have two options available, lv 10 and lvl 16. Do I need to unlock higher lvls? And under bonus it's always "adventurer in need (tank)". Does this mean only if I play as tank I get bonus reward? About pets, I currently have 3. Two dps and a tank one. Do dps ones do the same damage?

Gear does need to be 100% spiritbound before it can be converted into materia, yes. Some gear cannot be converted even then - the tooltip should include "Convertible: Yes/No" indicating if it can be converted or not.

There are many different duty roulettes, each of which will take you into a random duty of some type.
Right now you likely only have two roulettes unlocked - levelling roulette which will take you into a random 4-man dungeon or trial and guildhest roulette which will take you into a random guildhest.
Each roulette will give a sizable XP bonus the first time you run it each day. (Exact size of the bonus depends on the duty and your level.)
If you are queuing as the role specified as "adventurer in need" you will get an additional bonus, which is not limited to once per day.