Hello snug,
Maybe you can start with 'intervals' or doublestops (i think is the official term), cause they sound a lot like chords. A interval is really just playing 2 notes as an interval. The most common are the major and minor intervals. For instance, if you play in the key of C, and you want to substitute a Cmajor chord ( C E G) , you can play a Cmajor interval which is a rootnote (C) and a 10th (E). If you want to substitue a Cminor chord (C Eb G), you can play an interval with rootnote (C) and a dim.10th (Eb).
In C scale, the Cmaj chord is the 1chord, and the Dm is the 2chord. To play the Dm you can use a rootnote (D) and a dim.10th (F) and so one for the other chords.
I like to play real chords (3 or more notes) also, but mostly in the upper registers of the bass.
Hope this helps!