If I had a juvenile record and now I am 24 and already married to a US citizen, what are my chances of getting a green card?

The immigration consequences of criminal matters is among the most complex areas of immigration law. Outcomes that were not "convictions" still may be treated as convictions by the USCIS; offenses that were misdemeanors still may be treated as felonies by the USCIS; sometimes a criminal case outcome/sentence can become modified long after the fact; etc. There really is no substitute for having an immigration attorney review court-certified copies of the disposition documents (charging document, plea, court finding, court sentence, compliance with court sentence, etc.) in order to provide a legal analysis and to identify the best course of action to take in order to achieve your immigration-related goals. And note, even if the criminal matter did not stand in the way of eligibility for a marriage-based immigration adjustment of status application, it would be necessary to provide court-certified copies of the disposition documents to the USCIS anyway. Some immigration law firms, including mine, offer legal services on a "flat fee" basis so that a client will know the total expense from the very beginning, and a few immigration law firms, including mine, offer an initial consultation free of charge.