Re barre chords, it depends on the song. Sometimes it needs it due to the key - if a song in C tends to use Am, a song in D will use Bm. You can go a long way without using them, but at some point if you want to play guitar more seriously then you'll need to get the hang of them.
I'm sure there's been a lot of threads about barre chords, but my tips are: (1) keep your elbow tight to your side so that your hand is rotated outwards into the right position; (2) don't use the flat of your finger, use the edge (about 45 degrees round) because the bone there presses down better; (3) keep your guitar pretty high up your body, because a low-slung guitar gets in the way of barres; and (4) keep working at it, because there's a large element of strength/endurance that just needs the relevant muscles building up. Also strum when you're practising barres to start with, because you won't be able to hold it down cleanly enough to fingerpick properly - when the strumming starts sounding good, switch to fingerpicking because that'll expose anything you're not quite doing right and get the technique perfected.
I think McGrath touched on something else earlier. When you're strumming your chords, try lifting one finger. See how it sounds, and see which ones work and which ones don't. Get a few of those down, and that should make your strumming more interesting.