Are you looking for starter decks?
If you're new I'd first off get every class to 10, beat each classes normal and expert AI (expert's not hard) along the way. This will give you a few hundred gold and you'll get the cards you require (eg blessing of kings, flame strike etc...) for climbing ranked.
Once you've done that I'd suggest trying out
trumps starter decks which require no additional cards. They are cheap and cheerful. You can replace a few cards as you get more for the class and turn them into other deck types (eg convert the warlock into aggro by dropping the curve).
If you're considering making cards then the best ones that are staples of nearly all decks are:
(2) fairie dragon - 3/2 untargetable with spells / abilities
(3) Harvest golem - 2/3+2/1 on death.
(4) Dark iron dwarf - 4/4 +2/0 on a minion (friend or foe)
Just remember you'll likely end up disenchanting a few if you make these, they appear in packs often as they are common etc...