Welcome to the forum, Paul!
Except for the guitar part (I don't play), I'm just ahead of you on this fun-filled trip. But hopefully some of what I've been discovering will be of help to you. (Experts, please correct my mistakes.)
What keyboard should I buy? This is to connect to the computer and also to learn to play on.
Only you can answer this question. Asking yourself a few questions will help point the way:
What kind of music do you want to play?
What kinds of instruments do you want reproduced most accurately?
Do you want the feel of a piano under your fingers?
How many different voices/instruments/sounds (i.e., piano, flutes, drums) do you want/need to be able to play at the same time. This is called multitimbrality. 16 appears to be the most common multimbrality by far.
How many different notes/tones do you want/need to be able to play at the same time? This is called polyphony. A quality keyboard will have a polyphony of 32 at the bare minimum.
Do you prefer an automatic or stick shift?
IOW, how much control do you want over sound characteristics? Some keyboards have more buttons and knobs than you'd find in the Space Shuttle!
What software will I need?
Some kind of DAW (digital audio workstation) software. Again, (and as with any software) what you ultimately choose comes down to asking yourself what you want and need:
Windows, Mac, or Linux?
How important is it to have a virtual, on-screen keyboard for editing?
Do you need the ability to see/edit musical notation?
Do you want to do looping? (Typically a .wav file is imported into your composition and used somewhat like an instrument by looping/repeating the sound.)
How many voices do you want/need?
Do you want/need to be able to edit during playback?
What kinds of plug-ins will you potentially want to use. VST is pretty common, and there is a fair number of free ones available. There are other kinds besides VST.
Do you want to be able to render and export to .mp3? Burn to CD? If so, note whether the DAW requires a you to obtain additional software for the privilege.
Are there different editions available? If so you, can save money by starting with a less featured edition, and later upgrading as your needs grow. Many people find the less featured edition to have everything they need and then some.
Is your computer powerful enough to run the particular DAW edition and all its features/plug-ins you need?
Will a free (generally open source) DAW do what you need? (Audacity is a popular example.)
Is a DAW provided with the keyboard? (I.e., some keyboards come with special edition of Cubase.)
Can you get support?
Do I need to change my computer sound card, or buy some kind of sound module?
You can probably start with the sound card already in your computer, and see how that works for you. However, at some point you may find yourself needing something significantly beefier.
Some people will say you need a spendy sound card from the get go. At this point I'm not so sure, given than many people, big name bands included, use a laptop with their keyboard(s). Laptops generally don't have top of the line sound cards in them, and you might be able to play back everything through your keyboard.
You might find that you are better off getting a newer computer, or upgrading what you have with additional RAM or another hard drive, etc. Even the fanciest sound card will not be able to perform well if the computer it's in doesn't have enough RAM or free drive space.
As an example, when I first fired up the ACID Music Studio demo on my rather aged 1.7 GHz, Pentium 4, Win XP laptop with 1 GB of RAM (2 GB when everything is working right... long story), I was quite amazed at how good it sounded... Through a decent pair of ear buds (Skullcandy), not the laptop speakers! (BTW, I have yet to connect a keyboard to my laptop.) The demo consists of 22 tracks of 9 MIDI channels (channel 1 used on multiple tracks) and 6 loops, and sounds as good or better than my favorite CDs.
As far as cost is concerned, I'm prepared to spend on quality kit, new or used, that will last me a while. Ideally, good value for money, rather than the most expensive gear.
Always a good plan!
BTW, I'm working on a keyboard comparison chart. Send me a private message if you'd like a copy. I will probably also make a DAW comparison chart.
