"Entry level" is somewhat subjective to what you're looking to get out of your bike.
A bike with a Sora drivetrain and alloy body will run you $500 or less if you can get a deal on Bike Nashbar or Bike Island. However, step up to the Shimano 105 and you're going to be paying upwards of $1k even with a decent deal.
Everyone here is also talking about entry level carbon, but you don't need to go that far. Especially if you're dishing out an extra $500 just to get some cheap carbon versus quality alloy + carbon fork. If we're talking weight savings, then you just paid $500 just to save 500 grams of weight on your bike since most decent alloy is already less than 9 kilograms. Carbon does absorb more shock which makes it easier on your hands and bum bum when going over bumps, but it's still not that big a deal. Remember that almost all bikes that you will look at nowadays will come stock with a carbon fork already. The extra dosh you're dishing out is just to get a carbon triangle.
If we're talking about things that are worth the money, then drivetrain is the most important. Sora and Tiagra are fine for entry level, but only the 105 is inter-compatible with the higher end Ultegra and Dura Ace parts for upgrade paths. It'll cost you extra to get the 105 versus the other options, but the drivetrain is the most important part so it's definitely worth considering. Though, to be quite honest, you're not going to buy Dura Ace parts and the Ultegra and 105 are so close in performance that, unless you want electronic shifting, you don't need anything higher.
The next thing I would consider is the type of brakes you want. Disc brakes will give you the best performance in unfavorable conditions like rain, snow, dirt, etc. and regular rim brakes will eventually wear out the wheels which are expensive to replace; whereas disc brakes clamp on cheap discs which can be replaced easily. There are also hydraulic disc brakes. Those who have used them will swear by them, and I think they're right. With drop bars, it's quite awkward to brake and puts some strain on your fingers if your hands are placed on the hoods, which is the most common riding position. Hydraulic brakes will just make it easier on you. Braking performance is the real takeaway from here. Not so much the wear on the wheels since you won't being doing it any time soon. The wheels might even die in a crash before the rims wear.
After those two things, I would then consider going carbon. However, at that point, a lot of bikes that come with a 105 or higher drivetrain and hydraulic braking will already have carbon frames.