I sent this in a PM to kleenur so as not to interrupt the admin discussion of whether or not the topic was appropriate for MERF, but since it's been moved I figured I'd share what I wrote in case other folks are interested.
In the interest of full disclosure, I figure that I should point out that I'm not really involved with my local SCA barony, but I am part of a non-SCA group interested in portraying medieval hunters, outlaws, and foresters, and I'm getting involved with the Atlantian Royal Forester's Guild. My historic persona (including but not limited to the SCA) is a 1350's English forester in Cheshire. I haven't picked which specific royal forest in the area I want to portray a forester in, yet, but I'll get there eventually!
The Osprey book is a good initial resource - those books general provide a decent broad overview, but not many specifics, and some of the illustrations have to be taken with a grain of salt if they don't provide specific citations. For example, they show 14th century archers using cloth arrow socks, but I haven't seen those depicted in artwork prior to the 15th century - they might know something I don't, though (but without a citation I can't know their source)!
For general information on 14th century England, I second Elleth and highly recommend
"The Time Traveler's Guide to Medieval England: A Handbook for Visitors to the Fourteenth Century" by Ian Mortimer. Not only is it very well written, it manages to provide both an overview of the rapid societal changes that occurred during the 14th century and small details, such as what a thatcher's mate would earn in a day and what sort of jokes the 14th century person would find funny. He hits all the major parts of life - food, clothing, money, travel, etc.
I have found less general resources for foresters. Part of the reason that my persona is based when and where it is is because I have been to Chester, walked the medieval city walls, and fell in love with the area, but also because Edward of Woodstock reintroduced forest law in Cheshire in 1351. The
"Register of Edward the Black Prince, Part III (Palatinate of Chester), A.D. 1351-1365" therefore includes the letter sent to the foresters of Cheshire outlining their duties, as well as complaints made by the locals in court when they could no longer use the forests the way they had for over 100 years (Ranulf de Blondeville issued a charter in 1215–16 setting more humane laws regulating use of the Cheshire royal forests). It provides more insight into what the foresters were doing than might be available otherwise (it has to be taken with a grain of salt, though, since the locals were very salty about the situation!).
For your outer persona (garb and gear), you could do worse than referencing Chaucer's description of the Knight's yeoman (
translated from Middle English) -
"A yeoman had he at his side,
No more servants, for he chose so to ride;
And he was clothed in coat and hood of green.
A sheaf of peacock arrows bright and keen
Under his belt he bore very carefully
(Well could he keep his gear yeomanly:
His arrows had no drooped feathers low),
And in his hand he bore a mighty bow.
A cropped head had he and a sun-browned face.
Of woodcraft he knew all the useful ways.
Upon his arm he bore a bright bracer,
And at one side a sword and a buckler,
And at the other side a dagger bright,
Well sheathed and sharp as a spear's point in the light;
A Christopher medal on his breast of silver sheen.
He bore a horn, the baldric all of green;
A forester he truly was, I guess."
You can see my interpretation
here, if you're interested. When it comes to patterning garb, you really can't go wrong using the
Bocksten man clothing. I've also referenced some the
Herjolfsnes artifacts, as well as illustrations from
The Romance of Alexander and other 13th-14th century manuscripts in my own gear. The 1407 edition of "Livre de la Chasse" may also be be helpful to you, since it shows hunters (pay more attention to the fellows handling the dogs or driving deer with spears, rather than the folks in fancy duds on horseback). Speaking of hunters, for more leads on primary sources, check out
Exploring the medieval hunt - not focused on foresters, but hunters are at least operating in a similar environment.
For a good general secondary source on garb, check out
Sarah Thursfield's "The Medieval Tailor's Assistant, 2nd Edition: Common Garments 1100-1480" - one of your local SCAdians probably has a copy, or you can find pdfs of the first edition floating about the Internets (I think one has even been linked in a topic here somewhere).
Gear is a little harder to document, especially when asked what folks in individual lines of work might have used, but
The Linkspages at Larsdatter.com is an excellent database of medieval material culture, organized by category. And of course, the
The SCA East Kingdom Royal Foresters Guild blog has a lot of information, as well! I personally disagree with some of the logical leaps they make on occasion (I'm a bit of a hardnose about documentation), but they always make clear what is document-able and what are their own scientific guesses based on evidence and their own experience.