Hello @jen0revision...
I think you need to write more examples... Choose a verb in the different endings and write that example to remember the endings...
The subjunctive is widely used to 'express wishes' in greetings cards, eg :
(Espero) que tengas un feliz cumpleaños...
or when you say 'bye' to something and wish them good luck...
'Que te vaya muy bien'...
Feel free to ask questions.