Opinions on worst Race/Class combination?

[Pyrocat]

If you've never played before I would suggest starting by picking a class that can solo at least somewhat: shaman, necro, druid, mage, shadowknight, bard, or monk. Pure melee (war/rog/mnk) are hard to level without twink gear or a solid leveling partner / groups, but Monks can at least make a passable attempt with feign death and mend. Enchanters can be great soloers but it takes a lot of skill and in-depth knowledge of the game, so they're not a great starting class.

As far as worst match ups... I'd say Erudite Paladin would probably be the most disadvantaged. Erudites have pathetically low strength, stamina, and wisdom scores which are the paladins primary stats. They also lack low-light vision and have a crappy starting zone with very few class appropriate quests.

However, there are plenty of race/class combos that are technically bad. Pretty much any race that has a low base stat in something that your class needs. For example, gnomes have crappy strength and wisdom, so a gnome cleric or gnome warrior would be a statistically bad choice. On the other hand, this also makes them more rare, so you can play them for the uniqueness factor (or because you like how gnomes look in plate).

tl;dr pick the class you want to play first, look at their available races (all classes have a picking the right race section on the wiki), and pick a race that doesn't have crap starting stats with your classes preferred stats, which the wiki will also explain. Also take into account other racial bonuses/penalties (e.g. iksar and troll have better hp regen, but also an exp penalty) and how much you like the look of the race. The most important thing is to pick something you think you'll have fun playing, not necessarily the very best stats.

p.s. picking anything other than iksar as a necromancer or a monk will probably make you kick yourself at higher levels, since the hp regen rate only increases at higher levels and can absolutely change the game for those two classes.