Ok here we go let see.....
Basic thing, gears= HP, defense, guard+ gears, no evasion+ stuffs. You goal is to get hit, if one mob can't touch you try multiple.
I got my monk to level 37 awhile back, long time ago. Guard was at around 30 or so. 1-30 shouldn't be hard when you are low level solo. No need to mention it.
Here is when I start skill up at level 60, wish I started earlier would made it easier.
40-80 in Yhoator Jungle. Link like 10+ Mandies and have them attack you while aiming at other mobs. 40-80 didn't took very long tho.
It took me around 4-5 days or so but only couple hours a day.
Back in the day, it was hard for monk to find a good party to level up. Also, static is way too slow; waiting for people to show up and so on. Big waste of time. So I decided to solo, faster exp and get skill up on guard same time. A friend quited, I kept his account for awhile before he came back, he is a whitemage.
I solo mobs with mule cure 80-110 guard, which is level 60-70. Mobs I fought was VT puks in woodland, then Crawlers + Diremite in Aydeewa Subterrance.
110-120 on them fish in Sea Serpent Grotto behind the mythil coin door all those mobs work.
After that I went to Davoid Play Orcish Champion.
This pic right here is why it suck try to skill up guard at level 75 even with - evasion gears. I skill up in Davoi from 120 till level 140 or so.
I start making gil, was working on Aegis. So everyday I camp behind Shahagin Door, where the NMs pop 15 mins. Made some good gil + alot of skill up.
The chart below
In the chart, there some other mobs also but all of them are decend to tough mobs at higher level. Sea Serpent Grotto not working anymore after over 220. After that it is all random but none of the mobs are below even match skilled me up. Most of the time after that, I skill up on VT IMP in mire. It is way slower but the EXP is greatest in game. I capped merits on all of my 9 jobs till they added more merits, both me and my friend char whitemage. I need to cap all 9 jobs along with the mule again later and more guard skill up when have time.
Skill up guard take awhile, but if you're up for it, it will cap eventually. Took me exactly one year and I'm only 233.7. I'll update later when I start on it again. Easy way to skill up, find a friend lower level then syn it up and get skill up faster, alot faster. Monk and Whitemage are bestfriends, need merits? find a whitemage friend cure5 and you go monk/war and fight imp. Counterstance rock. I can't tell you exactly how benefit guard will be yet, since the only real answer is at 269 guard skill + gears.
Here is so much for guard.