If Sharpshooter and Ragin Goblin are the only creatures you plan to use, then don't use the Raging Goblins at all. They'll functionally be a Shock that turns off after a couple turns.
Lightning Bolt, and X Burn Spell (only need one set) Shock and Burst Lightning are all standards for Burn decks. After that since you're not going for tourney play you can add goodies like Flame Javelin and Firebolt and Fireblast.
Also Browbeat: They either take 5 for three mana or you draw 3 cards, it's up to them. In a dedicated burn deck the opponent should always pick to take the five, but 5 for 3 isn't bad.
The list is really quite large for casual. The important thing to remember is to burn the opponent, not his creatures. Unless he gets a utility creature like Life gain or damage prevention, the damage is better spent at his head. Burn is about racing.