Forger - There are mainly two popular builds for crafters,
Bard26/Figh4/RDD10 and
Wiz21/Bard19. If you have two crafting hammers then any DC wizard can become a crafter, but if you don't want to rely on any items then those are your two main choices. Just make sure that you remember to sing every time that you forge, I know somebody who has messed up multiple times by forgetting to sing first.
Fighter - My personal favourite DPS build is a
Figh12/WM25/Rog3. Any monster or area that I can solo with a cleric or mage can also be soloed with this build. It can even beat a lone Umgah Royal Guard, although two at a time is too much for this build when solo. While this used to be useful on all high end PvM runs, Driller has made some changes to boss runs so that there is no single DPS build that is best for every boss. The closest that you will get is a
Figh12/WM25/Pal3 which is useful on almost all of the boss runs. Due to a lack of UMD it isn't as capable of soloing as a Figh12/WM25/Rog3, but in a party it is usually the better choice.
Mage - There are so many choices for a PvM mage that I can't recommend a specific build. In general, aim for 36-38 caster levels, 38 INT/CHA, and ESF: Necromancy. Wizards will be able to fit in a secondary focus, Sorcerers are probably best off sticking to Necromancy. Some people like to make AC Sorcs with Auto Still 3, but AC doesn't really matter for PvM, HP does. A gnome with 18CON and 18INT/CHA is a good starting point for a PvM mage. If you are new to mages I recommend making a generalist Wizard first, to test out what spells are useful and where. If you are experienced with using mages on BSK then go for an Illusionist Wizard or Sorcerer.
This applies to all PvM casters, but especially mages, make sure that you pick up Mummy Dust. Some monsters are magic immune and some monsters require a distraction, the mummy is the best summon for dealing with them. It can also do most of the work while levelling, so try to get the feat early on if you can. Dragon Knight is nice but it only lasts for two minutes so only choose this feat if you already have a mummy.
AA - There are plenty of choices for AA's too, although they usually have a hard time soloing and are better off levelling in parties. There are two types of AA, divine AA and non-divine AA. A
Sorc2/Pal8/AA30 is a minmaxed divine AA built for high end PvM runs, but it assumes that you will have a party to shield you.
Bard10/BG3/AA27 is another divine AA, but this one picks up Devastating Critical at the cost of Divine Might damage. For non-divine AA's, I recommend either a Monk9/Wiz2/AA29 or a Bard9/SD2/AA29 since both have useful defence mechanisms. If you want to use your archer in high end PvM runs then a divine AA is best, if you want to solo then a non-divine AA is best.
Cleric - My two favourite PvM clerics are easily
Cler38/Monk1/Wiz1 and
Cler38/Monk1/Rog1. They can solo almost everything that is soloable and can be used as healers on high end runs. There are plenty of alternative cleric builds too, in general my advice for mages applies to caster clerics too. You want 36-38 caster levels, 38 WIS, ESF: Evocation, and a Mummy Dust summon. Prioritise HP over AC, a Gnome with 18CON and 18WIS is a good starting point.
If these are going to be your only builds then I would recommend either making an arcane and divine crafter or editing one of the above builds to have crafting feats. For example, the Wiz21/Bard19 has all three crafting feats and so can make any arcane wand or scroll (assuming that you are a generalist Wizard). A DC Wizard can easily fit in crafting feats too, so you could choose a Bard/Figh/RDD crafter and a generalist Wizard with crafting feats for a mage. The Cler38/Monk1/Wiz1 gets Scribe Scroll for free, so adding Craft Wand (and Brew Potion if you want to) will make it a useful divine crafter.