Won match only got base exp

If you could provide the like to the game, or the amount of exp you got, the game length, and game type, or screenshots.

This would be a lot easier to help you make sense of with any of these.

There is a first win of the day mission that gives xp, xp bonuses you can purchase in the store, and the base xp for playing the game.

The base xp is calculated from queue type, duration of the game, and if you won or lost.

http://leagueoflegends.wikia.com/wiki/Experience_(summoner)