Personally I think that History of Benalia is a must for any aggro deck, but I can definitely understand if you want to keep it budget.
As other cards you might or might not want to include in your sideboard, I suggest Adamant Will for combat tricks and Luminous Bonds or Seal Away. Ixalan's Binding could also work but of course you can't bring an answer to everything with aggro (and 4 mana can be taxing).

Hope this helps! If you are interested, I also tried to craft a monoWhite Knight aggro deck before GRN. The difference was mainly in the fact I focused on Knights to use History of Benalia third effect and to exploit the active ability of Valiant Knight.

Hey ZanarDusk thx for the messsage! I realy have a problem with hyped card's and benalia is a powerful one .. Most of the deck is for option but i agree with you in that case. I got intrested in what case i would use luminous bonds/seal away ?? In place of baffing end? And adamant will? pride of conquerors??

Again, thx for opinion

Luminous Bonds is a relatively cheap spell (moneywise and manawise) that you can maindeck to deal with powerful attackers and blockers, I think it will pay off in a deck with many small creatures where a strong blocker could become a problem. However, it also deals with creatures that have triggers on block/attacks like Etrata, the Silencer (the RVN one), Star-Crowned Stag (albeit, I'll admit, I made 2 poor examples as those cards are seldom seen in the current metagame).
Slaughter the Strong can be useful in those same istances, but you usually want to save it for board clear against things like a kicked Verix Bladewing.

Seal Away In particular is really strong when you want to answer something during your opponent turn, as white usually lacks instant removal.

You should definitely keep Pride of Conquerors, I think, as a +2/+2 to all your creatures in a deck such as yours can easily be a game breaker.