If you can learn about eight chords more or less and learn to use a capo, you can play in any key you like to sing in simply by capoing. You need to master the intervals in the simple major scale, which are usually counted by half-tones. From C to D is two half tones. From D to E is also. But if you observe the white keys on a piano starting from one of the "C" keys you will find that the scale of C, which is all white keys, has the following intervals in half-steps:

--2-2-1-2-2-2-1
C-D-E-F-G-A_B-C


All major scales have the same pattern of INTERVALS regardless of what notes they contain.

THe total is 12 half tones making up an octave. If you like playing in C, for example, but you need to sing in F, you have to raise the tone 5 half-tones, which means you put the capo on the fifth fret and play C chords to make sounds in the key of F.

I KNOW this may LOOK complex, but if you break it down to fundamental concepts and get your arms around it, so to speak, you will indeed suddenly find yourself being able to transpose any played key into some other sung key with relative ease. Studying the notes on a piano keyboard will help.

Amos