Racials really dont make that much of a difference.
That said, it depends on what kind of character you're building. If you want a spellcaster, the best picks are high elf, breton, or dark elf. If you want a melee character, go for wood elf, khajiit, or redguard. If you want to tank, go for orc or nord.
The bonuses are as follows:
Spellcaster Races
High Elf
+Magicka Regeneration
+Max magicka
+Fire/Frost/Shock damage
Breton
+Max magicka
Reduced Spell cost
+Spell resistance
Dark Elf
+Max Magicka
+Max Stamina
+Fire Damage
+Fire Resistance
Physical Races
Khajiit
+Health Regeneration
+Weapon Critical Chance
+Damage when stealthed
Harder to detect while sneaking
Wood Elf
+Stamina Regeneration
+Max Stamina
+Disease/Poison Resistance
+Damage when stealthed
Harder to detect while sneaking
Redguard
+Stamina Regeneration
+Max Stamina
Restores stamina on melee attacks
Tanking Races
Nord
+Max Health
+Frost Resistance
+Health Regeneration
Reduced damage taken from all attacks
Orc
+Max Health
+Max Stamina
+Health Regeneration
Reduced Sprint Cost
Improves all charge abilities
Argonian
+Max Health
+Disease/Poison Resistance
Bonus to healing received
Imperial
+Max Health
+Max Stamina
Restores health on melee attacks
If you want to be good, never listen to these kind of people. Racials are VERY important.