Richie, be thankful you did not spend the $300. There is so much available today without paying a large amount of dollars.

Try playing a simple song -- only two chords --in five different keys--take note of their relationship. Memorize, no misuc.

Next try three chord songs, which there are many, keep looking for things in common.

Examples; How to use a numbered sacle.
"C" Major scale-- C D E F G A B
Using numbers--C=1,D=2,E=3,F=4,G=5,A=6,B=7
You will notice that G or G7 leads to C.
Or use numbers, V leads to I.
Using the V leads to I means;
In the key of "G' D or D7 leads to G V to I.
In the key of "F" C or C7 leads to F V to I.

Three chord songs; C F G or I IV V
It will not be long before things clear.
John C,