What is a Kit?
When I talk about building a kit for the SCA, what I mean by kit is the set of equipment that is necessary for you to be involved in your chosen activities in the SCA. All kits will involve garb, as every person is required to make a reasonable attempt at medieval clothing. However, there are other objects that can also be included in your kit. The particulars will vary on these as an armoured fighter's kit will involve armour. A rapier fighter's kit might also involve some armor (like a nice gorget and gloves) along with their swords. An Archer's kit might involve a bow, quiver, period arrows, etc. Those who don't do any of these activities but camp a lot with the SCA on the other hand, may find that for them a kit means a tent, camp furniture, etc.
Choosing a Persona:
The first step in putting together your kit is to identify a particular place and time that you are interested in portraying. For some this is relatively general (14th century France) for others it is highly specific (Swabian landsknecht from 1560). There are several factors worth considering in choosing your persona. The obvious ones are whether you have a particular interest in a certain place or time and whether you want to fit in with a local group that tends towards a certain period (like the 14th century mafia in Atlantia or Calontir's anglo-saxons). However, when attempting to keep costs down, it is important to consider the balance between looking good and having the resources to achieve that look. In general, the later in period you go, the more complicated and fitted clothing gets, the more difficult the armor gets to make, and as a result, the more time or money it will take to make your kit.
The "One True Century":
This last concern was the reasoning behind my first baron's explanation of the popularity of the 14th century mafia. The SCA minimum armor standards essentially require rigid joint and head protection, however early medieval armor doesn't provide this, while later medieval and renaissance armor involves a greater degree of more difficult to make plate armor. During the 14th century, however, historically accurate armor meets SCA standards and also can be made to look good by someone with minimal skill. Meeting SCA minimum standards with earlier period armor relies on hidden sport armor, while later period armor simply requires more complicated work. Garb also follows the general trend that the earlier in period you go, the less fitted the garments are, and so the easier they are to pattern. pre-14th century, you can make pretty much everything out of rectangles and triangles. By the 15th century, much of the clothing requires fitted curves in order to achieve the right shape. This is not to say that later periods are impossible, just that they are harder. For those whose primary interest is not in making things, it may be advisable to choose a persona for which it will be simpler to make and acquire the basics of a kit rather than to choose to portray a persona for which the appropriate gear will take a greater degree of determination. For the purposes of this series, I'm avoiding the assumption that anybody wants to make their own things, but rather I am assuming that the reader understands that they may need to make their own things. I will attempt to keep things simple for that group.
Things to Consider Including in your Kit:
Garb: This will include not only clothing, but also footwear and accessories as well. I will make a post about accessories in the future, but suffice it to say that without appropriate accessories and footwear, most SCAdians simply look like they're wearing some weird pajamas. For inspiration, take a look at the Armour Archive's 2013 show off your "soft" kit thread: http://forums.armourarchive.org/phpBB3/viewtopic.php?f=16&t=158437 (Soft kit usually refers to garb, as opposed to armour which is hard)
Armor: Matching garb and armor in a single kit gives you greater flexibility in terms of which clothing you wear to an event and allows you to stretch the number of outfits you have. It also helps your armor fit better, because often, armor was made to be worn with a particular kind of clothing. Keeping your armor pieces consistent with each other and consistent with your clothing is the most straightforward way of looking awesome. I recommend taking a look at the Armour Archive's show off your kit thread here: http://forums.armourarchive.org/phpBB3/viewtopic.php?f=2&t=160509&hilit=show+off+kit
Feast Gear: For the most part, my instructions for feast gear will be to pick up some cheap wooden salad bowls at good will, but an authentic feast gear kit can really help build the medieval experience at feast.
Tools: These are going to be discipline specific items such as archery equipment, musical instruments, puppets or other props for performance arts, etc.
Camping Gear: This would include tents, camp furniture, beds, cooking gear, day shades, etc.
Miscellaneous: There are probably things I have forgotten, however banners displaying your heraldic device are a common thing to have in the SCA and might be something you want to help make you, your encampment, or your day shade look pretty.