Any discount, 99 cent, dollar tree similar stores in Madrid or Barcelona?
 

I'm moving there and i find it difficult to come by inexpensive toiletries and such,
I guess cereals, and basic stuff would be nice, thank you

Yes there are.

Traditionally there are stores mainly run by Chinese where they sell cheap goods, not necessarily at 1 euro. You can't miss them as every district seems to have one.
Also there are "Todo a 1€" stores where most goods are priced at 1 euro or 99cents. There are chain stores called DOMTI where everything is priced at 2 euro or less, including toiletries.

Yeah, the Chinese Bazars have cheap crap. Literally crap. I bought a pair of knock-off Nike Socks that said Ñike on them. Even though they are tube socks, the toes on them are crooked. I think I paid a Euro for three pairs.