Adriano >
1) Adding to what Ana Nymus said, number marking in language can be entirely optional, or even completely absent (that is, the nouns never change for number, but of course you can give quantity indication with separate words like "some", "many", "two", etc). Some languages also only mark plural on some sub-category of nouns, but not on all nouns. This map gives a good overview:
http://wals.info/feature/34A#2/25.5/145.7 (you can also click on the "Occurence of Nominal Plurality" grey button to get a detailed description of each possibility).
There are also a lot more ways to mark plural than the use of suffixes:
http://wals.info/feature/33A#3/-1.44/71.672) For gender, I think one thing you need to clarify is whether you want
lexical gender or
grammatical gender (or both!)
Lexical gender is gender that is specifically that of the referent, of the actual thing being refered too by a word; English has lexical gender: we talk about actors, stewards or policemen if we are refering to men, but about actresses, stewardess or policewomen if we are refering to women — this depends of the real thing we are talking about, not directly of the words we use (that is, if the words can indicate gender at all — most English words can't, this is mostly limited to job nouns, and to singular third person personal pronouns: he vs she vs it).
Grammatical gender is a property of words that is completely independent of what is being refered to: in French "victime" is feminine even if the victim is male, and "serpent" (snake) is masculine even if it's a female snake; gender is a fact about the words themself, not a fact about the things the words refer to. Grammatical gender generally implies
gender agreement: adjectives, articles, pronouns and/or verbs will have to "match" the gender of the noun they are refering to. Here's an example from italian:
Un lento treno è passato = A slow train has passed.
Una lenta machina è passata = A slow car has passed.
"treno", train, is masculine, "machina", car, is feminine, and you can see that the indefinite article, the adjective, and even the past participle change form to match the gender of the noun.
Most languages that have grammatical gender
also have some degree of lexical gender, making things more complex, but there's nonetheless an important difference between the two.