Here's some of my cheap thrill hauls.
Fifty peso plastic shades at the sidewalk stalls around Ever Gotesco, Commonwealth (these cost more than double inside the mall)
Ten peso hair clips. The white ones are ten pesos for two pairs but I already lost the other one.
Ten peso eyeliner pencils.
I love nail polish so at 10 pesos a pop these ain't so bad and the staying power is pretty decent considering the price. There's just this slightly more chemical scent to it. Oh and try to check the brushes, I got one that won't spread evenly.
Remember the quality of the products in these small tiangges are not really guaranteed so I guess the best tip is to haggle and to check...check...check.