Well, for starters, if you are a summoner, you need a feat (spell focus Conjuration) to take Augment Summoning. To make this not a waste of a feat slot, you want conjuration spells that need a save, grease fills that 1st level slot
Second, grease can be used on an area to slow opponents as they trip and fall, DC is 16 in my example sorcerer. It will help any rouge in the group because anyone who falls in Flat Footed thus sneak attack able
Third, it can be used to grease a weapon, making it hard if not impossible to use. Barbarian is coming at you with his great axe in rage, grease, can not use his great axe as it slips out of his hand. Useful for ranged disarming opponents
The thought of using the favored class to gain bonus spells is good, but since in levels 1-3 you can only gain 0 level spell (states it must be a level lower then the highest you can cast) I don't see the point in taking it before level 4
If you want a direct damage sort of sorcerer, I recommend the Dragon or Elemental bloodlines and change the first 2 feats to Elemental Focus and Greater Elemental Focus with a type matching your chosen one in the bloodline (Burning Hands at 3rd level would be a 3d4(+3 if a dragon bloodline) "fire typed" 15' cone with a DC 17 to half)