Hi there.
Do you have a VPS? What O/S are you running (usually its CentOS or Ubuntu ) on it?
I'll optimize your VPS first, update wordpress, phpmyadmin, mysql etc. Close any unnecessary ports (for security ), install Webuzo (to easily manage your VPS) or cPanel (license required. I recommend webuzo).
Then, I'll optimize your WordPress, make it SEO optimal, remove unnecessary plugins etc.
I am proposing $200 as I am new on freelancer (I do have old profiles on other freelancing websites, which I can tell you upon request). Edit: Since you set your budget at 250-500, Freelancer is not letting me bid $200
if you want, I can also give you a good VPS
Dont pay if you are not satisfied!
Regards