@ShneekeyTheLost has a good point. If you're overwhelmed by the amount of stuff in modded minecraft... Try a lighter pack. Learn those mods. Then add to your list of mods you're comfortable with.
I agree with those who say your "mistake" is playing an Expert mode modpack, which is for veteran modded minecrafters who are bored and looking for a good hard challenge. Infinity Evolved is a great modpack, just don't play the expert mode as a beginner! Learn the ropes the easy way first.
As to your question regarding a base... Infinity Evolved is one of those modpacks which alters the normal Minecraft villages (I do not know which mod does it), adding more buildings, adding guards who will attack mobs (but not you), and most importantly of all... adding a wall around some (but not all villages).
What we found (I played the pack on a multiplayer server) is that these walled villages make a GREAT base. It's kinda cruel I suppose, but I killed all the villagers, razed all their buildings, flattened the interior, and then patched up the wall where it needed it... bingo - instant fortified base! Most of these walled villages are fairly large, mine was almost 4 chunks by 4 chunks on the inside, plenty of room to build all sorts of stuff.
So try that out as a suggestion. But a lot of us have the same problem you described - I am NOT a good builder. My stuff looks like crap to me, and I'm almost never happy with my base layout. Nobody is ever gonna see my base and go "WOW, that is awesome!" I'm more of a practical minecrafter - the stuff I make works good, but it doesn't necessarily look good. LOL
I actually think Big Mac has made a really good point here, and more can be made of it.If you are really set on building a nice base first, you could just hop into creative mode. Sometimes I start a modpack by building a giant base that I like in creative mode, and then I go into survival mode and play it like a normal survival series. I don't actually spawn anything like machines or ore or anything that would ruin my progress of the game, because that ruins the fun for me. I just get my base looking nice then I go out and punch trees and stuff like a normal first night in minecraft survival.