i used to do that kinda stuff all the time. when i was in year nine i started a business with my friend, and we printed tshirts, and made little dresses
. we were planning on selling them at markets, but ended up selling stuff at school.
i got some $3 grey mens singlets from a chinese junk shop in rockdale. i'm wearing mine now! they're really long and the armholes are so low that you can see my bra/underboob but they're awesome for bumming around in. they have a nice low neck which is cool too.
i've been thinking of getting some more and sewing seams along the sides, so i have a singlet-dress, but i cbf.
asian junk shops are the best places to get plain things. this one in hurstville (if you are in that area) sells massive oversized tshirts for 2 dollars each, the only complaint i have is that the fabric is a little too rigid and not sheer enough for my liking. i'm sure that you could get them somewhere like campsie or earlwood as well though.
here's some ideas:
-get a really oversized tshirt, and cut the top of it to change the neckline so it's more of a singlet shape. overlock the edges or leave them raw, if you like an unfinished look, or seam the edges. then sew a piece of elastic in the middle to give it a waist (or just leave it and use a belt if you are lazy). and voila! you have a little dress. it can look kinda boring if you do it with a white tshirt, but cute if you use a stripey one or one with a nice fabric.
-use bias binding in an interesting colour on hems if you want to make something plain more interesting (this wouldn't really work on a jersey or tshirt fabric, but it works perfect on cotton)
-also, lace or broderie anglaise type trimming is really cute to use.