Having (slight) trouble with guitar.?

In standard diatonic harmony there are only two major 7th chords, The I and the IV. ii,iii,and vi are minor 7th, V is a dominant 7th (standard 7th chord) Vii is a minor7b5 (half diminished) here is the harmony of the C maj scale in 7ths. Cmaj7 Dm7 Em7 Fmaj7 G7 Am7 Bm7b5. The most common progression is the I-IV-V but the jazz standard is the I-ii-V (usually referred to in jazz circles as the ii-V-I) These are very good starts for improvisation. I recommend playing each of the chords on the low three strings first (6,5,4) covering the bass register. Than do the same on the first three strings. Using both the I-IV-V and the ii-V-I will give you a good idea on how arpeggios can function to develop a unique melody and bass line. Once you have developed some coordination within the basic shapes than you can combine different bass and treble "arps" together to create "custom voicings" Try playing a I chord in the bass register and switch to a IV chord in the treble register. Then play a ii chord in the bass and switch to a V chord in the treble. This is an example of combining arpeggios to create interesting melodic ideas.