Everything starts with an interface. Well, a computer isn’t bad either, but I assume you have got one already. If you want to record analog instruments you need a thing that converts your instruments output into 1 and 0 to be able to enter the digital world, an interface.
It depends on your requirements how many input and output channels you need. For me, two input and two output channels are sufficient, it should support line level, instrument level and microphone level signals to be ready for what ever instruments to come. I have got a Steinberg UR22 which fully pleases all my needs! It’s connected via USB and very convenient. It just works well! It also works well with effect pedals in front. I have lot’s of them and I cannot live without. Fine to have modulation, reverb and delay as digital plugins, but Fuzz should stay analog Fuzz, I think! And it it works well with these as well!
Most of the time the interface comes with a free version of a DAW, which is the next essential part for recording digitally.