what class and weapon build is best in the game?

There is no best class, it's all about what equipment you have.
READ:
http://ladderslasher.d2jsp.org/index.php?g=2
Pick a feeder class, learn the weapons it can use, and the corresponding str/dex ratio.
Gather gear for each tier from III to XIV.
Weapons you want enhanced effect, armor you want ee (enhanced effect means better tanking) or stats (means more damage,) charm you want stats. Accessory slot is only good for enhanced effect. So a heal charm there.
Remember, if you can pass the master quest, your next class will be samurai! They use swords/daggers. Plan ahead.

to be honest... there is no reall BEST toon / items to start with.
Basically once you choose the toon, the items that you require will come into effect.

Example: I play Hardcore, so the toon I choose is Guardian, for a few reasons:
1. They use chain / plate armor only and that gives the best physical defense.
2. I only use STAT armor and charms because the STAT starting numbers are better than any other Feeder toon...
... for survivability, and if done right, you deal decent dmg and heal yourself with the Guardians Abilities.
3. Chain / Plate state armors are cheaper... this also includes Clubs and Heal Mastery gear (chains / plates)
4. If you are stuck solo'ing by yourself, you are still able to MQ even with low ee gear, and if you use Medium HM gear it is better.
5. The Heavy weapons are underestimated, they can be very useful with Guardians... they use ALL Heavy weapons.
6. there are many other things that can change things from #1 through to #6... you have to decide based on your timezone and other things.

GL in your endeavours.