One mistake many "newbies" and more experienced people commit when researching is one that has been commented on countless times here, but let's do it again!
This only really works if you have limited your interest to a certain time period.
When researching for things you want to make, do broad research. If you love sugarloaf helms, by all means, use chef's suggestion for the time period. However, when you want to extend your kit for that period, and want to research, look for general trends, not a spesific piece. Thus, don't pore over a thousand illuminations looking for a certain piece of armour from that period, pore over a thousand illuminations and get an idea for what was commony used together during that period.
Same goes for civilian kit - if you want to do a late 13th century/early 14th century impression (and I sat GO! to that

) and want a surcotte to wear outside your tunic, don't pick out a certain style you want and try to document it - instead, look over the sources and see what appears. If you like a certain type of surcotte and find it in 4 of 550 illuminations, all late in the period, chances are it's not too representative.