One of the biggest problems I have in game is that I have no clue what to build mainly because I don't know what kinds of items are out there. Is there anything out there that can help me to learn the items or is it just game after game that I have to play to learn the right builds? Any ideas are welcome and thanks in advance!

http://www.sporcle.com/games/thecupid/dota-2-items
heres a quiz that tests you on the names of items by what they do
this will get you thinking about the specifics of items it even gives little fun tips and comments : D

I know when i was just starting out dota 1 i would just copy item builds i saw work really well alot.
In terms of builds for specific heroes theres always going to be items that are better on some rather than others.

But certain items are amazing for specific roles like mek or force staff is great for supports blink dagger for initiators battlefury on your farming melee carries (for the most part at least) and scythe of vyse is amazing in general. One thing i can tell you is that when you play a game look at what the enemy team has for heroes and think carefully about what you might need like if they have alot of magic damage think about a pipe or a cloak or if they are all physical damage think about a ghost scepter or some armor. Like i said Mek is always amazing on just about anyone (really haha) items are going to vary each game because each game has different heroes and is always going to be different from the last. its alot of practice but theres some common conceptions you can go into a game with!

Well one of the things I ran into the last game I played, was that one person had already built a mek and I was lost on what else to build. Late game, is it better to go for personal items like say blademail and veil of discord rather than do multiples of like pipe and mek?

Yeah once your "team core" items are done (mek pipe drums) are done just do what you or your team needs.

Possibilities are:
force staff
euls
drums (multiples arent the worst because the stats are amazing)
Ghost scepter (if they have ALOT of physical damage)
BKB if you can get it
Veil (like you said) if you need to amplify your teams magic damage
Heavens Halberd (if you need to shut down an enemy carry)
Hex (if you can get it)
Necronomicon (really versatile item, doesnt need as much micro as you would think)
Vlads (if your team doesnt have one for your teams melee carry) you dont necesarily need the lifesteal but its good for the team
Blademail (if you keep getting jumped, either the enemy will still go for you anyway but sometimes theyll ignore you completely)
Rod of Atos (the slow is good, and it gives stats but its expensive and bkb stops the slow so go for something else unless they dont have bkbs)

thats about everything i can think of.

I left out things like linken sphere and shivas only because theyre more items you kind of just pick up because you can you dont say hey im going to rush a shiva's guard it kind of just happens

It really depends on the hero your playing and who you're playing against. As to learning items, you just have to play a lot to be honest.

This plus communication between your team. Its been said before and will be mentioned again, team communication is key here. The last few games I have played, I've taken upon myself to ask what everyone is doing at different stages of the game. Trying to get a feel on what route each of my team-mates is going for and try to plan accordingly. that way we don't double up on a Mek and such. I know this may not be the best way to go about it, but it makes people talk to each other and that's very helpful.

Aye, and also who your playing against and in turn how well they are doing also comes into play.

The only problem I have with this quiz is that you need the EXACT names with proper spelling. Sure I know that an item that gives 80 attack speed and has a chain lightning ability is mjollnir, but can I spell it without having to look it up now that is the real test.

Also figuring out all of the short names or slang names is kinda important. Sure you probably know what a bkb or mkb is, but if someone said get a rod of aui_2000 it gets a bit more complicated.

Mjolnir

That is exactly what I'm talking about in dota its with 2 L's but in EVERYWHERE else its 1

HOW DARE YOU MISSPELL THE NAME OF THE HAMMER OF THOR!

Yeah Thor is kind of a big deal!

Don't kill the messenger valve is the one who started it.