Some input on choices:
Kyosho V-one-RRR
- drives very, very nice out of the box with the basic setting
- newest 1/10th
- Kyosho hopups are more expensive. Replacement parts are reasonable though
- It's Kyosho. Wait a year and the one you have now will be obsolete. Little or no support in English from Kyosho.
G4
- Parts tend to be expensive and hard to come by but this varies heavily depending on market
- There is a perceived bias against the car which I believe is due to it's Taiwanese origins. Ignore this. In the right hands, the G4 is a decent competition race car.
- Is there support for this car from Team Magic??
MTX-3
- Drives well out of the box and tends to be easier to setup. It's very stable.
- One of the oldest 1/10th on the market. Lots of hopups available
- Just started their English language forum this year. Quite a ways to go yet
- Some adjustments (like camber) are a PainInTheAss
- Mugen is bringing out the MTX-4. If Mugen is your choice, wait.
Serpent
- Very flexible in terms of setup. Know what you're doing and you can get a killer setup
- Too flexible in terms of setup. Don't know what you're doing and the car can be a real nightmare to setup
- Lots of option parts . . . mainly from Serpent
- The best English language support site on the web. Includes one of the best setup books I've ever seen in an RC kit
- Drives very stable out of the box but you'll need to fiddle to get a killer setup.
If the guys who win at your track drive any of these 4, consider choosing that car and asking for setup data. It can take a while before getting really good setup data so copying someone else at first can save you a lot of time.
The suggestion on LHS is good but keep in mind the Internet is also an excellent source of parts. Serpent seems to have the right idea in selling you a single pack of replacement plastic parts for front and rear although I'm not sure that would change my mind about what car to buy.
None of these cars will drive you to victory by themselves. You'll need lots of practise to do that. There is no magic car that works perfectly. They all have weakness. Your skill as a mechanic/driver will determine race results.
As for engines, the Nova-Mega is very reasonably priced and many initial problems have been fixed. On the other hand, the more expensive engines like JP and Max can give you an edge if you are already a good driver. Max is definitely an ultra fast engine but I have found it hard to get a really optimal tune out of it after a while. Brand new though, it's hard to beat in a one-on-one on a straight piece of track. Novarossi is also a good choice although I prefer the simpler carb of the JP engine. JP is definitely a good engine but very expensive. Take care of it and you can use it a long time with very good results.
Good luck.