Firstly a magnifier or you'll struggle to see the parts. Some use a head worn version like me, but anything that will magnify and can be used hands off will do.
A supply of sharp blades to remove the parts from the fret
A decent small flat file to remove any spurs
Some good quality tweezers to hold small parts. I have some surgical haemostats which are basically locking tweezers for clamping blood vessels which work well, but any good tweezers will do. You may need to spend a few quid to get some good ones but it is very difficult to work small PE parts without a pair
A good flat surface and a Stanley knife blade for folding. I use a combination of the Stanley blade and a scalpel to make folds. For forming or rolling round parts I simply roll them around the shank of an appropriately sized drill bit. I've never used one of those expensive folding 'machines'.
Now you've got your PE part ready to fit you will need a few more bits.
A glue applicator is essential to get small amounts of glue where you need it. You can make one by taking a sewing needle and cutting the top off the eye leaving an open U shape. Stick the sharp end in a cork or something similar or you will definitely end up sticking it in yourself! The U will enable you to apply a drop of glue to the relevant place.
Fresh CA glue (Superglue) is usually best for attaching PE parts. If you think you need some wiggle room then an acrylic glue like Gator's Grip will also work.
An accelerator for the CA glue. I have one which can be wiped onto either the part or the place where it is going. This causes the CA glue to react very quickly and when the part is offered up it will stick instantaneously. There is NO wiggle room and you only get one chance, but you don't have to struggle to hold a minute part in place whilst holding your breath
The most expensive thing on the list is probably the magnification, but it's something you will use for modelling generally and you may well have it already. The same goes for most of the rest, standard modelling equipment entailing no vast expenditure.
This advice from Richey is very important:
'When cutting tiny pe parts from the sprue stick it on masking tape first it stops it pinging off and getting lost to the carpet monster.'
Ask me how I know
Cheers
Steve