¡manos a la obra! = за работу :)
И снова Испанский :)
ALGUNOS goes with a noun, ALGO never does. The first one is a determiner, the second, a pronoun:
"Tengo ALGUNAS LIBRETAS en mi mochila" (As you see, it goes with a noun, libretas. This is a femenine noun, and that's why we put algunAs. The meaning is SOME)
"He tenido ALGUNOS PROBLEMAS últimamente" (This time, problemas is a masculine noun, so we put algunOs)
"Tengo hambre. Voy a comer ALGO" (Here, there's no noun accompanying "algo". Here, it means SOMETHING)
So, the word to be put depends on the appearance of a noun or not (ALGUNOS/AS if there's a noun, ALGO if it doesn't), and in the case there's a noun, you have to look for the gender of the noun.
Also, don't be confused. The singular of ALGUNOS or ALGUNAS (in Spanish you can write "ALGUNOS/AS") is ALGÚN:
"¿Has visto ALGÚN GATO?" (Here, the noun is gato (cat). As it's singular, you have to use ALGÚN, not ALGUNOS/AS). Besides, and answering your question, there's no distinction of gender in singular.
As you may be a bit messed with all this, this is a summary:
DETERMINER (it goes before a noun)
· ALGÚN (Singular, for masculine or femenine)
· ALGUNOS (Plural, for masculine nouns)
· ALGUNAS (Plural, for femenine nouns)
PRONOUN (it doesn't accompany any noun, it SUBSTITUTES one)