If you're primarily fighting meph, cold resist and lightning resist are paramount (and poison/fire for in the durance). For cold and poison you could always go the thawing and antidote potions route, though it's kind of a pain for continued boss running. For lightning if you cant afford anything expensive, try something like:
1 Ring + 1 Perfect Topaz + 1 Rejuvenation potion = 1 Coral Ring 21-30% Lightning Resistance
There are others as well.
1 Ring + 1 Perfect Sapphire + 1 Thawing potion = 1 Cobalt Ring 21-30% Cold Resistance
1 Ring + 1 Perfect Ruby + 1 Exploding Potion = 1 Garnet Ring 21-30% Fire Resistance
1 Ring + 1 Perfect Emerald + 1 Antidote Potion = 1 Jade Ring 21-30% Poison Resistance
One perfect gem of each type with any amulet gives you resist all, but with six perfect gems you could trade for some pretty good items, so I wouldn't reccommend that one. On the trading forums there will periodically be someone cleaning out their mules for a certain type of gem (or rals or junk jewels), and you can get pretty good items for almost nothing.
Taurgon said:
There are some low lvl rune weapons that can help also.
For bosses, crushing blow is extremely helpful. Bonesnap, Crushflange, Fleshrender (uniques), Black (Thul+Io+Nef in a three socket gray text flail), and Strength (Amn + Tir in two socket gray text melee weapons) are good and inexpensive. I would reccommend Black, as it's fast and has 40% crushing blow. Guillame's Face, a helm, also has crushing blow on it, as well as Gore Riders and Goblin Toe unique boots. You'll still need decent damage, though, as crushing blow only works well until 1/3 or 1/2 health.
And what realm (and ladder or nonladder) are you? I might be able to help with basic mf stuff.