Your recordings are only as good as the signal chain you use to make those recordings and there's no more important element in your signal chain than your microphone. This article is about one microphone that will certainly get the job done and which is not outrageously expensive (although it is not cheap either.)
The mic in question is the Shure KSM44. I write about this condenser microphone from my own personal experience with it as it has been the principle mic in my home studio for seven years and I've used it to record a variety of sources during that time.
First let me describe what a condenser microphone is. It's a type of mic that is generally used for recording sources such as vocals and acoustic guitars (these are the two sources I most frequently record with the KSM44) and which requires a preamp in order to work. Almost all audio interfaces come with a preamp so you're probably already set in that regard, although you will get a better sound by using an external preamp such as the Art MPA Gold.
There are actually two different categories of condenser mics, one is a large diaphragm and the other is a small diaphragm. Large diaphragm condenser mics have less noise and capture lower frequencies better. They also tend to be more expensive. They are usually used on vocals while the small diaphragm mics are often used on instruments with a lot of high frequencies (such as a violin.)
The Shure KSM44 is a large diaphragm mic and it's also a "multipattern" mic. What's multipattern mean? There are three different patterns that mics can record in (and the KSM44 can be switched between all three.) Those patterns are cardioid, figure-8, and omnidirectional.
A cardioid pattern means that it only picks up the sound coming from front of the mic while rejecting sound coming from the back and most of the sound coming from the sides. A figure-8 pattern picks up sound from both the front and the back while rejecting the sound from the sides. An omnidirectional pattern picks up sound from all around. Each of these patterns can be useful in different recording situations which is why it's so cool that this particular microphone can be switched between each of the possible patterns.
Many mics boost certain frequencies in order to "color" the recording in some way. While this can be quite nice in certain circumstances, having a mic that has a more neutral (or "flat") response can give you a lot more versatility. The Shure KSM44 condenser mic is known for it's neutral response and this is one of the big reasons why it's such a versatile mic. It can be used to record just about any sound source effectively.
Like all other condensers, this mic requires a mic preamp. The preamp can greatly effect the quality of the your sound and investing in a good quality preamp should probably be your next move after getting a good microphone. Like I mentioned above, most audio interfaces do have built in mic preamps but you'll get better results from an external preamp.