I think you are spoilt for choice on this, but it does depend on the style and level of game your looking for.

For a skirmish style of game then as @templar007 has said, Saga for me is the best choice.

If your looking for an army level recreating the battle, then Hail Caesar from Warlord Games and the latest supplement for the dark ages is very good.

Another good set of rules for an army level which is very enjoyable is To the Strongest. This uses playing cards instead of dice and also uses a grid for movement. I was sceptical about these things until I played it and I found it good fun.

There are many others out there, Sword Point, DBM, Sword & Spear, Clash of Empires and many more.

If you want something cheap and less time consuming to begin with…

start with the scale you want to play and then work backwards, the best set (if indeed you can find a best) will be largely dependent on the scale you use. By scale I mean scale of game not miniature size as the two are not always the same.

After that it’s a case of deciding what kind of a game you want, a light pick up and play or a very granular simulation will shift the goal posts again.

I love Saga as a skirmish game, but if I want a historic version of Hastings it is balls. So you need to set parameters for yourself, otherwise we could probably list rulesets until the cows come home and it won’t get you any closer to what you’re after.

The mechanics in To the Strongest and Basic Impetus would suit the period

Try

https://freewargamesrules.fandom.com/wiki/Freewargamesrules_Wiki

as there maybe something there that you like