I don't think he, as a beginner, has access to things like Berze clip, DI, and holy armor...

Well, GC Crusader... you need much INT, INT raises your magical attack power, and GC depends on this mATK. Then get a strong weapon, something with much ATK. A Haedoggum is a very good weapon, since it gives you +3 INT to your stats and it has like 120 ATK, I think.
INT will raise your Heal power as well. Yeah, as a GC Crusader, you'll need Heal lvl 10, because GC hurts yourself.
So, let me tell you the skills you need to get:
Skills:In order to get GC, you'll need the skill Faith lvl 10, then Holy Cross lvl 6, and voilà : GC. For Heal, you need Cure lvl 1, Divine Protection lvl 3, and Demon Bane lvl 5. GC and Heal on lvl 10, if you have enough Job Levels for it.
Swordman skills: Sword Mastery lvl 10, Increase HP Recovery lvl 10, rest doesn't really matter. Skill Bash lvl 10, Provoke lvl 5 to get Endure. Quite useful.
Stats: Well, I'm a lvl 96 Crusader, I can only tell you which stats I have:
BASE Str: around 30-40
BASE Agi: 1
BASE Vit: 25-35 (yeah, not too much).
BASE Int: 90-99
BASE Dex: 50-60
On a lower level, you should leave Str at 20, vit at 20 or 25, get like 50-70 INT, and rest into DEX.
Equipment:Since you're not that rich (I believe

), you should just get anything that gives you good DEF, like a Chain Mail, for example. Some NPCs sell it, I think.
Headgear? Helm. If you find a Helm[1], slot a Elder Willow card into it (+2 INT).
Shield? Shield[1] with Andre Egg card. Small HP boost.
Footgear? Sandals[1] with Zombie Prisoner Card. Yeah, I know, Undead will hurt you more, but you'll get more EXP from these monsters.
Accessories? Earring[0]. Gives +2 INT. Or Ring[0]. +2 STR.
Places to train:On a low level, go to Payon Dungeon lvl 2 and 3.
If you think you're strong enough to kill stronger monsters, go to Glastheim Prison and kill Zombie Prisoners and Injustices.
You can stay there till the 80-90s.
Nif2 with the Lolis is a good map too, but these enemies can do high damage to you, so I don't suggest it to you at first.
Down in the Pyramids, Ancient Mummies are undead too, they give splendid EXP, and are a bit easier to kill than Lolis. I still mob and train there.
Well, to sum it up: Stick to undead and shadow monsters, so your GC will always do nice damage.