I think I mentioned this in the other thread, but my sewing skills are nil. Well, I can sew on a button or repair a hole in a sock (which will be visible and ugly) but that's it. So if you are learning to sew, I bow down to you! That's always been something on my bucket list. I believe the various sewing supply stores (Joanne Fabrics, Singer Sewing Store) offer classes for beginners. Call them up and ask if they know of anything.
For me, I try to purchase as many elements of my costume as possible. So if a character wears modern/basic clothing, then I can search around and find what I need 'off the rack'. For example, I am trying to put together a costume from Walking Dead, and I just searched around for the clothes I wanted online. No sewing required!
I have made a few things, like belts, with a glue gun. Not as professional as sewing, but a lot easier to use. You have to test it on the fabric first, because sometimes it works and sometimes it doesn't. Another trick I have done is buying that industrial strength stick velcro, and using that to hold things together. I have also painted a few items (props, boots) with spray paint, and even (boy, was I proud of this) made my own stencil from cardboard and used t-shirt paint to paint a logo on the front of a shirt. So yeah, I've cobbled along and managed to put things together.
For the costume you have shown, I would say the only thing you would need to 'sew' would be the tunic. And if you find a plain tunic you like (even one where you could just remove the sleeves) you might be able to 'glue gun' the light green panels on, if you didn't want to sew. The arm wraps can actually be just wrapped the day of, and the black armbands can be strips of leather with a snap/hook on it, or you might find something similar in a store. I think you'd be able to get the shoes in a store or online, and you could paint them to match if you needed to. The pants look very much like a pair of pants my husband has as part of his Renaissance Faire costume. I'd check places that sell that kind of clothing and see if you can find something similar.
ETA I just had a thought. The top is basically a long tank top. If you find a tank top you like in that olive color, you might be able to use fabric paint to paint on the lighter green 'stripes'.