At small points I would use a cannon and an organ gun or 2... stay clear of grudge throwers until you hit larger games (where you find the larger units- great targets for stone throwers).... bolt throwers are just personal preference, but get a cannon first (or more).
Thunderers are basically going to be the heart of your army- they are better then quarellers but have less range and are much more static, so having a unit or 2 of quarellers by the time you hit 2k is a good idea. At 1k I would probably take 1 unit of quarellers and 2-3 of thunderers.
As for unit size, that depends on personal preference- bigger units have more stand & shoot menace but if they get caught in combat you lose a bigger unit (but vice versa its easier to wipe out an entire unit if its smaller- and only fully destroyed units give you any VP in 8th). Personally I would stick with the minimum units of ranged models and just have many different units- keep them close enough to support each other, but not close enough for multi-charges or overruns to allow 1 enemy unit to destroy 2 of your units in a turn.
Warriors are always a must for dwarves- a block of them is solid and means you have something to counter those units that do make it to your gunline (you can just take more guns instead, but odds are something will get through- and solo-gunlines tend to die rather badly once the enemy reach them). Always give any dwarf a great weapon if you have the option- you lose +1 off their armour save but the added 2 strength is a godsend, meaning you'll actually do something. Dont worry about the ASL, dwarves pretty much have that as an army special rule anyway (ok, same/higher I as ogres, some undead and the odd nurgle daemon... but not a lot). The dwarf army is built around the idea of getting hit, surviving, then hitting back hard... so they still work exactly as they always should have (even if you now have the chance to get charges off).
