The first thing I made was, obviously, a petticoat. Coincidentally it was so well made that it's lasted with me throughout the years and is still among my favourites, only needs a starching every once in a year or so. Petticoats are nowadays easier available and cheaper too so for a beginner lolita they'll probably pose no big a problem, so let's say you already have one. What next?
A simple skirt.
You don't have to immediately/ever deck yourself in full burando (unless you want to, of course), especially if you're not yet certain whether or not the style even is for you. The good sides to having a basic ruffly skirt as the first item are that it can be worn outside of the style as well, if you make it yourself you can make matching accessories to it which immediately up the "loliness" of it, it's easy to coord because you'll only need a nice blouse or a shirt, tights/knee socks and cute shoes - which btw can totally be offbrand as well. In all my lolying I've worn f.ex. ballerina flats, a pair of Dinsko pumps I tuned up a bit with a couple of pears, nice black buckle shoes for my short goth period, a pair of simple thick-heeled black shoes and so forth.
And of course skirts are among the easiest possible sewing projects, in which regard they're only beaten by the -
A lovechild of a ruffle skirt and an apron. It's not an ideal first piece because it always requires a skirt to be worn underneath, but making a few apron skirts will easily broaden your wardrobe. Wearing one over your skirt will give the skirt a whole new look, therefore having a couple of these available offers lots of new opportunities for coording. Again, making one comes with the possibility of making matching accessories so there's that as well.
Another suggestion for accessories is to get fake flowers and make some yourself, preferably hair accessories since having some makes a big difference in the whole look. If you use easy to coord colours such as white, off-white and black you'll never be lacking in accessories.
Jumperskirt, in other words a JSK
Another easy to coord and variable item, definitely one of the best options for a beginner. Wearing a different blouse underneath and matching the other colours of the coord accordingly will allow for many different looks with simply one item. An OP (one piece), though they're lovely, limits the wearer a little bit when it comes to coording because so much is already there, and while it may feel like an easier thing to wear it's actually the exact opposite. Just because a dress seems like a fully realized outfit does not mean it is that, and besides if there's no chance of varying a look it'll quickly become boring.
TL;DR a beginner lolita needs:
* a petticoat, first of all
* a few cute blouses
* a cute pair of shoes (beware too tall and narrow heels, they can work but most often they don't)
* simple accessories: bows, hair clips, roses etc.
* tights or socks, can be simple
None of the above needs to be expensive. I've got lots of my wardrobe straight out of secondhand stores, fleamarkets, vintage shops, ordinary clothing stores and so forth. All of the above are also not necessarily lolita only -wear but can be used for various looks and occasions.
For the lolita items, good first buys/projects to make are:
* skirts and JSKs
To broaden your wardrobe an excellent choice would be:
* an apron skirt - I'm putting together a tutorial on how to sew one so stay tuned if you're interested!
* all head accessories have to have an option of tying or pinning them securely to the hair
* bloomers are good for all year round - they literally protect your ass against both cold and surprise!storms
* cardigans, get yourself some cardigans, seriously seriously do it
* or cute sweaters