I was told that I should start by befriending a lot of people at the party.

How long should I be talking to the first group before moving on? Or should I just stick with one group until they get bored?

Making friends at praties is the best solution for sarging alone.
I also have some problems with sarging alone but I got the whole idea fixed up in my head.

You should open the first set you meet or encounter. try some small talk - and not only girl set, but also a guys set so you could always get back to this set if you mess up in other sets.

And it also creats the illusion that you aren't alone, your with friends. and those are the friends you mention in false time constraint.

You asked: I think that your the one that makes this decision.

and also: Never let them get bored, If you feel that they are getting bored - ROLL OFF.
You can always get back to them if you already met..

hope it helped you,
cheers

Some advice I want to give you for parties where you hardly know no one

first
Its the easiest form of night game going
-Its so much easier to open , keep track of your target and f-close all in one night

when opening , I would start with the guys first ( my own preference other people may have different insights)

I just say " Hey , I just wanted to say thats a cool tee shirt , where did you get it from ? "

If you want to elaborate on that talk about the shop , area or if its sports related
with guys always head towards sports or cars or beer , easiest way to make guy friends

you've got some social proof now go talk to some girls or get the guy that you've talked to to introduce you to some people

other easy openers
" wheres the cups at ?"
"wheres the toilet? "

- elaborate on that by thanking them and then saying you didnt expect their accent / voice to sound like that , this usualy sparks curiosity so just go into a conversation on how you can usually tell how people sound from the way they hold themselves or the way they dress .

easy as pie

and for how long should you stay is up to you , just try and leave the group on a high

Basic game plan , I know you didn't ask for most of that I just thought it might help a bit