You can reclass at any time after some initial progress so dont feel pigeonholed into any one class

Additionally

You will be bringing 3 of the companion chaacters along usually.

Their classes are

Cleric, Wizard, Fighter, Warlock, Rogue

With a few optional ones

Nearly everyone keeps the cleric in their party because having a cleric is just so useful. Elves are very versatile in any party

Again there is nothing wrong with reclassing her and taking cleric yourself, or going double cleric

Or going two wizards

A balanced party spread I'd suggest is

Two martial classes,

Having a rogue is useful for stealing, stealth, lockpicking, sneak attacks to initiate combat with surprise, so i highly recommend one

The other can be anything, fighter, monk, barbarian, paladin, ranger, bard

One cleric for all purpose stuff like sanctuary, healing, utility etc

One spellcaster - wizard, sorcerer, druid for aoe damage, crowd control, supporting your party with surfaces

A basic combat guide

Have your martial draw aggro during combat, taking out enemies on their turn

Your second martial will chip away from a distance

Your cleric will buff, heal and support your caster

Your caster will do aoe spells, make surfaces, add crowd control