'ain't' is slang and isn't used in normal conversation, unless you speak slang all the time! I think they're not really saying 'I got'.. (that's incorrect so it does sound like slang, yes..) It should be "I've got", which is similar to "I have" Maybe they're saying it quickly, or not carefully!

I agree with Keith, 'ain't' is slang and you should say: I've got or I have got. You can also use have on its own, but without 'got'. In questions: Have you got....? or Do you have?

Saying "I got" is grammatically incorrect; however, it is used commonly. Although you wouldn't say it in a professional setting, it is not as slang or "low" as saying "ain't". You could say "I got something for you" to a friend/family and it would be very normal and acceptable. If you wanted to say a similar sentence in a professional setting, you would say "I have something for you".

One thing to keep in mind is that "have" is more passive and "got" is more active and done with intention. "I went out and got a job." sounds like you made it happen. "I went out, and now have a job." sounds like it could been something that just happened to you, accidentally perhaps.

I won't say "got" is slang but uneducated speech used in the old days by slaves. It is OK in informal or casual speech. However, It will reflect on your standing in the eyes of others, especially those who are sticklers in high places. You never know how you are being watched by others. Why jeopardize your career chances? Other examples, "no ticky no washy" or "long time no see" but are used in daily conversations between close friends etc. Of course, one has to see in what kind of situation it is used for, perhaps to drive home a point. Then the listener at least will know that you understand the culture of the language. "I Got You Babe"... famous song from Sonny and Cher! https://www.youtube.com/watch?v=BERd61bDY7k