That packet of needles looks like a good set. I really like glovers needles for any soft leather repair or reinforcement. Harness needles and an awl are perfect for harder leather.

I few meters of those threads would be great. Upholstery thread or button thread is very good to have for webbing buttons etc. The standard stuff for lighter fabrics.

I take a business card and fold it over itself (glue in the middle), cut a spool shape in it and wind on various threads. Works great.