Depends what sort of party you prefer. I like magic-heavy parties, and I found that necro, cleric, dark elf, dragon and vampire suited me very well. If you prefer more might, you could consider one or more of a troll, a knight, or a minotaur.
However, you only create one character in this game; you select the others from among a number of pre-designed characters you come across during the game. With one exception, the stronger ones won't join you until you've completed some of the quests; the stronger the character, the more has to be done before they'll join. I played one game in a way that allowed me to get the most advanced characters as quickly as I could, but this had two disadvantages. First, the game was too easy, and second, I missed out on the fun of getting my characters promoted. I found that I had most fun by taking low level characters and sticking with them.
It's very tempting to start with a dark elf as your created character, but you can pick up a first class dark elf (Cauri Blackthorne) quite quickly, and I usually start with either a cleric or a necro. You can pick up a cleric, a necro, and a vampire in the village where you start, and you meet a knight before you leave the area. What I usually do is to swap the necro or the cleric, depending on which my created character was, for Cauri, and the knight for a young dragon to get my final party.
MM8 is a smaller game than MM6 or MM7, but I enjoyed it — I hope you do, too.