First of all, welcome to Final Fantasy XI! =D
I'm not the most experienced FFXI player around, but one thing I recommend is to learn how to use the auction house (AH). You should sell items you don't need there, instead of selling to the NPCs, buying stuff at the AH is usually a good idea as well.
There are auction houses in all of the starting towns (Bastok, San d'Oria and Windurst), as well as Jeuno, and maybe some other places.
Another thing to keep in mind is that it can be a bit tedious to play solo after a while, so if you're having trouble gaining exp you should look for a party. I played solo until lv16, but then again some jobs are harder to solo than others.
Since you're playing as monk it should be relatively easy to solo until at least level 10 I guess.
Also, you can change job at any time if you visit your mog house in town.
That's all I can think of right now, I hope it helps ^^
Zeronova - Hume - War23
Darknova - Tarutaru - Blm4