Just as in English both may be interchangeable in certain situations but not in all. If you walk into a store and say "I would like to have some water" (conditional "me gustaría tomar un poco de agua") or "I wanted to have some water" (past tense "queriá tomar un poco de agua") both would convey the same meaning. But, since "quería" is past, it can be used when talking about the past, Last week I went to the theatre, I wanted to take pictures, but it was not allowed. La semana pasada fui al teatro. Quería tomar fotos pero no estaba permitido. In this case, it is clear that you could not use "I would like to" (me gustaría) instead of "I wated to" (quería). Other than that, they are used the same way as in English, just keep in mind the tense difference and you should be able to know when both or either one can be used. I hope this helps.

"Me gustaría" is in the future. "Me gustaría tomar un café" - "I would like to drink a cup of coffee" "Quería" is in the past. "Quería tomarme un café" - "I wanted to drink a cup of coffee"

I believe you may have made a typing mistake. If I'm wrong and you meant "quería", the first answer is correct. If I'm right and you meant "querría", then both can be used in the same situations. "Querría" is literally "I'd want", while "me gustaría" is "I'd like". They're exchangeable, but I think "me gustaría" is, when placing an order slightly more polite. Just slightly.