Ok theres people in my family that get told by aunties that if you pray X dua/name of Allah/surah/etc Y many times on such and such time/day you get a certain benefit or help from Allah.

Now I don't know where they come up with these, because every other day my mum tells me that so and so auntie recommends to pray whatever it is how ever many times and I've never heard of these ones in the sunnah.

The only ones I heard of to be valid is praying surah waaqiah for rizq and the tasbeeh of alhamdollilah x33, subhanallah x33 and Allahuakbar x34. Correct me on these as well.

But what about the rest of these that are said to gain all these different benefits are they allowed? or even mentioned in hadith?

which ones are the corrects ones you can pray for specific things such as sustenance etc

^Well, if you pray Surah Mulk, it'll save you from the punishment of the grave, likewise, if you pray Surah Kahf on a Thursday niight or on Friday, you'll be safeguarded from the fitnah of Dajjal... And yea!

There's many other suwar and tasbeehat with different virtues! Like there's one particular Istighfaar, that if you pray it three tiimes on Friday before Fajr, all your minor sins will be forgiven.

Hope that helps!

There are lots and lots of Surahs and Adhkar that have benefits. I'll put down some which I can think of right now:

1. Surah Yaseen - Reciting it once gets you the reward of completing the Qur'an ten times and whoever recites Surah Yaseen at night with the sole purpose of pleasing Allah then he will be forgiven and if he persists in reciting it every night and dies, then he's a Shaheed. (I'm not totally sure about the Shaheed benefit.)

2. Surah Sajdah is to be read along with Surah Mulk at night for prevention of the grave's torment.

3. Surah Mulk is to be recited every night for protection from the grave's punishment and it also intercedes for your forgiveness.

4. Each name of Allah has some benefit with it and so its like you have to say a particular name like Ar-Rahman or Ar-Rahim or Al-Hadi after Salaah and those names get benefit according to the quality mentioned in the name.

5. Reciting Ayat-al-kursi after every Salaah provides protection for you till the next Salaah.

6. Surah Waqia'h for Rizq and I also read that the one who recites it is counted among the people of Jannat-ul-Firdaus but I think that comes from a daeef or fabricated Hadeeth.

More coming soon

Can you lot above me say where you got those from, please, coz I think that's what his problem was, as in ppl tell him such and such without proof and bruvs confoosed coz e duno if they iz from the sunnah or not innay.

The Prophet's (saws) sunnah is stuffed full of different dhikr.

http://www.geocities.com/mutmainaa/dhikr.html

Unfortunately, it's a geocities page and will occasionally be over it's limit, but keep checking back.

Well, I had once found a very beneficial post on another forum giving out the rewards of reciting some Surahs of the Qur'an but I couldn't find it now. But there's this E-book which has good information in it with Duas and rewards of Surahs.
http://www.central-mosque.com/sunnah/sunnah_duas.pdf