The choice of your audio interface is going to depend on many factors. So here are some things to consider.
Remember the three 'Ws'
Compatability
If you are going to buy your audio interface as a bundle with DAW software of your preference, then, you have nothing to worry about. If you are buying the interface independently, then, make sure it is compatible with the software you are planning to use.
Connections
You may be connecting only your own equipment to the interface, in which case, you should have an idea of what connectors you need. However, you may also be connecting other people's equipment as well. If you have options on the interface you are buying compare the connections they have. For example, USB, Firewire, Thunderbolt.
Input/Output - Quantity
Remember the three 'Ws', this is where it matters. Think of the number inputs you may need at any one time e.g. how many microphones and musicians.
Input/Output - Types
As well as the number of inputs you need to look at the types offered. For example:
Studio Organization
One thing that really helps with efficient studio workflow is having an organized studio. As you begin to purchase more equipment for your home studio things can get out of hand. In large studios, most equipment is rack-mounted. If this is how you plan to expand, then, you may want to purchase a rack compatible interface.
Focusrite is a company with a long history of making pro audio products for more than 30 years. This is one of the reasons why the Focusrite Scarlett 2i2 is one of the most popular 2-in/2-out USB audio interfaces.
There is now a 3rd generation version of the Scarlett 2i2, with upgraded features on the preamp design, improved inputs and outputs including a USB-C port. plus other improvements that make the 2i2 an even better investment.
The initial set up of the Scarlett 2i2 is made really easy as it comes bundled with a selection of many of the most popular software including Avid Pro Tools First and Ableton Live Lite. Focusrite’ also provide their quick start tool, providing popup prompts and also supports customized installation through a webpage.
This interface offers high performance, Focusrite's years of design experience leading to its very low latency that you would expect on a much more expensive unit. It is great value for money.
This is another of the 3Rd generation Scarletts a big brother to the 2i2. The 18i8 accordingly has 18 ins, including 8 ADAT ins and 8 analogue outs if you need more ins and outs. The 18i8 has the same Focusrite quality and performance but with more to offer than the 2i2. Still great value for money.
As an alternative the PreSonus Studio range has comparable offers to the Focusrite scarletts. There are many configurations to choose from across the 12 units and like the Scarlett range they are USB compatible and include a good software bundle.
Universal Audio is another industry stalwart. having over 60 years experience in audio design. The Apollo x4 will give musicians all they need for a desktop analog studio and is bundled with UAD analog plug-ins and LUNA recording system. It has 4 Unison enabled preamps and has elite-class A/D and D/A conversion. The Apollo suite of interfaces are class leading interfaces winning many awards for audio hardware.