Welcome to the LOC!
Here are my opinions and others will probably log on and give you theirs. Each has his own particular likes and dislikes, just pick the ones that suit your situation the best.
Since you just got this ES, I would takes it to a Lexus dealer for it's first oil and filter change and in the process tell them you just bought the car and ask them to look it over while checking the fluids, tires, brake pads, etc. After that, I personally do not trust a Jiffy Lube or Sears etc. for regular maintenance. I prefer to take mine to the dealer because in my humble opinion, even though it cost more, I feel they know more, catch more things, and in my dealers case, are honest.
As for parts, many on here use Lexus, Toyota, and aftermarket. Generaly posting your situation and parts question here can get you an expert recomendation.
I had a 2005 ES330 and I used 89 octane gasoline with no problems. Here in the midwest I used Amoco and other major brands.
Hope this helps.
Paul