Originally Posted by: icebreaker1588
I'm working on chord progressions and I need help with some theory.
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You need to understand how chords & scales are related to each other. First make sure you really know this stuff.

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Then go to this intro to music theory for how chord progressions are built & function.

http://www.guitartricks.com/tutorial.php?input=495

Finally, you need to know that chord progressions are built the way they are because they follow the melody of the music.

Originally Posted by: icebreaker1588Most of these chords you learn at the start are boring. You can only play them so many times before you feel the need to omit or add notes.
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That's why we learn triads & inversions. There is no getting away from playing basic major & minor chords for as long as you play music. But learning triads & inversions opens up the whole guitar to virtually limitless voicings of those basic chords so they aren't just the same old thing.

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[QUOTE=icebreaker1588]
Well what if I want to use a chord like C#mno5addD or D/F#? Where do I find online or any kind of resource for using these kinds of chords?

Chords & chord progressions come in two basic flavors:

1. Functional
2. Ornamental

Both of them are ways to make the voices (the individual notes) of the chord move as melodies.

To use your example, you'd play a D/F# if you want to hear the bass line move from G to F# to E in this chord progression.

G - D - Emin

If you play those chords in root position you get a bass line that follows the root notes:

G (leap up to) - D (leap down to) - E

|--3----2-----0------------------------------|
|--0----3-----0------------------------------|
|--0----2-----0------------------------------|
|--0----0-----2------------------------------|
|--2----------2------------------------------|
|--3----------0------------------------------|


But if you use the D/F#, then you get a particular different flavor with a linear descending bass voice motion.

G (step down to) - F# (step down to) - E

|---3--2--0----------------------------------|
|---0--3--0----------------------------------|
|---0--2--0----------------------------------|
|---0--0--2----------------------------------|
|---2--0--2----------------------------------|
|---3--2--0----------------------------------|


It's all about the motion of the voices; how the notes of the chord move. And once you learn inversions, then you can play those chords up or down, in any direction, any place on the guitar that you want to! 2 examples!

|----3---5---7-------------------------------|
|----3---7---8-------12---10---8-------------|
|----4---7---9-------12---11---9-------------|
|--------------------12---12---9-------------|
|--------------------------------------------|
|--------------------------------------------|

To answer in a more general sense!

How do you know when to use a given chord? When the melody outlines it or suggests it (functional), or you want that particular sound in the music at that point (ornamental).

How do you know if the melody outlines it? By playing a lot of melodies & chord progressions to see & hear for yourself how it works!

Have a look at these basic classical lessons that explicitly show how melodies are supported by chords. Very simple stuff, but you've got to walk before you can run. I wish I could convince more beginner guitar students to really grasp this stuff. So many people want to just play something, or play more weird chords. Then eventually they wonder why they don't really understand how music works.

This stuff is how music works!

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How do you know if you want the particular flavor of an odd chord? By playing a lot of weird chords many times & remembering the sounds categorically so you can play them as needed.

These jazz tutorials will give you a great insight into how some "weird" chords actually make a lot of sense once you understand how they are functioning.

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[QUOTE=icebreaker1588] Or even better, what knowledge of theory do I need to understand to be able to know my options and build a progression without help?