I have been inspired to play this game again. Was dam close to the end when I gave up the last time over a year ago. Started from the beginning with a new build thinking about dex this time, any advice? Also where and when do's the DLC start? And at what soul level and point in the story should try the DLC? thanks.

You get access to the DLC when you are going for the Lord Souls (after beating Ornstein and Smough). There will be a crystal golem near the beginning Duke's Archive with an item that allows you to access the DLC areas. DLC is best done around this time too.

Edit: Oh yeah, don't put any points into Resistance.

Knowing where to start the DLC is pretty darn confusing and convoluted, as you'll need to kill the hydra by the lake below Darkroot Garden, then go back to the lake where you killed the hydra and find another crystal golem (this time it's a golden golem), kill it to release Dusk (but don't kill her). You may need to reload the game for this event to trigger. Once you've released Dusk from the golem, reload the game again and head back to the edge of the lake where the hydra was and you should see a summoning sign, activate it. Now go to Duke's Archive and find the only blue crystal golem that resides within the Archives when you enter from the elevator from Anor Londo, kill it and take the broken pendant, now go back to the lake where you first encountered Dusk and the crystal golem and you should trigger the DLC.

Much like what Vinny did in Load Our Last Souls feature, I played the DLC after beating all the bosses except for the final boss (because after doing so will end the game immediately). I would say to do the same because there are some bosses in the DLC that are pretty difficult or at least do it after you have the Lord's Vessel. Not much more I can help since I started as a DEX build but then switched to a STR build mid-way through. I guess just concentrate on dumping most of the early points in END so you get more stamina/equip load, that has been my focus when levelling up my characters.

You're going for dex so what weapons are you planning to use? Rapiers, Katanas, Scimitars, Whips and Scythes are all dex based weapons with fun and different movesets, find something that you like and upgrade it!(better going for the normal path and avoiding all the elemental stuff since the scaling would be better in the long run).

Katanas are better for damage, scimitars do less damage but are faster to swing, rapiers allow you to attack while holding your shield up, whips are not that particularly great and the great scythe is probably the best dex weapon damage-wise.

I usually use buffs when I make a dex character, so when you reach and high level(>100 or more) you may wanna dump some points in faith or intelligence, but don't worry about that for now.