Hi not sure if I can help but, when I make garments I use the serger to finish the seams off, it cuts the material even and gives a professional look to the garment.
If you look at garments you purchased, you will see that the serger thread shows. I think thats just the way sergers work.
I have a four thread serger, and I can run mine with only one needle the only diference I see, is instead of two seam thread's you get one.
Just keep at it, and try all kinds of ways of doing things, and you will teach your self a technique and gain experience.
You can buy something that has all the bells and whistle, but if you only need whistles, what good are the bell's and, if you only need the bell's then what good are the whistle's? "Bragging rights" as my husband would say.
Be of good cheer.