This is tricky - the first two models I had were built for me by my father (a Matchbox Strikemaster and Huey Cobra) but the first I built myself were a Frog Bf-109 and a Frog Bf-110. I’m not sure the 110 really counts though, since it was the night fighter variant and those antenna were not a good place for a five year old to start, and the end result was…not good. The first I built myself that ended up with a kit to glue ratio higher than one was probably another Matchbox kit - either the Alpha Jet (which was a very good kit for a five year old to build) or the Matchbox F4U.