I assume you haven't played V2's ultimate mode. Man, that was much, much more difficult. I'm not trying to make a point or anything, but man, Lv80 on Ultimate on V2 was insane.
However, the GCN version's Ultimate mode really is much easier. My FOmar got to the caves offline at Lv62 with no trouble.
However, I have a whole lot of experience with Ultimate, so that doesn't really mean much. ALSO, FO always had a much easier time in Ultimate at first because of their magic. In V2, magic was really the only way to do damage at first because all other attacks usually missed or did PATHETIC damage. Luckily, it's relatively easy to lots of damage with weapons this time around, but FO still have a big advantage early on due to the fact that their magic is pretty strong around this point and never misses.
So, I'd recommend you level up in VH online and get to Lv80 before you try it offline, if you're having problems. That's the required level for playing Ultimate online anyway, and it's a pretty good level to begin Ultimate mode at, in my opinion.
Otherwise, yeah, just use every bit of PSO skills you can muster. Jellen and Zalure are a great combo when paired with Shifta and Deband, especially so on Ultimate. Always try attacking monsters from the rear or flank, never from the front unless you're sure you'll kill it. Never get surrounded, etc. Use common sense and skill, and it shouldn't be too bad. In my opinion, as long as something doesn't kill me in one hit, then it's never too hard to play.
Best of luck. There's nothing like finding your first Ultimate mode spell or rare.