Is there any guides somewhere, or is it even someone who specifically mf's?

its not quite cut and dry as a typical d2 mf char.
there is a higher drop % in the catacombs rather than in the arena
potentially any char can be a "mf" char if you stack it with +magic luck items

You can always make a good weller character. I would reccomend the rogue caster, if you have good int armor and weapon with a good charm and heal charm you could do wells and hopefully something good might drop out. If not you can always transmute the items that you get.

Here's a good guide showing how to build a good rogue caster : http://forums.d2jsp.org/index.php?showtopic=21842652&f=272

How much fg would i need to make a succesful rogue caster?

If you want one that can do well's easily also, about 2-3k

This is considering
40+ Intel Weap [500 Fg+]
40+ Intel Armor [500 Fg+]
150Ee Charm [Around 1.5K]
100+Ee Heal [Around 300]

You would also need to gain the melee gear up to about 40, and then some casting gear from 40+

But then again, this is only if you want a crazy good weller, that can also mq fast. If you want a good rogue caster it can cost cheap you would just need to grind some bit

all chars tha can do well are going to cost a good bit.