What age do you all think is appropriate to date?
...when you are ready to get married to somebody that you see as a potential spouse.
Dating in itself is useless. WHEN and at what age depends on countries, societies and laws...and then of course of the maturity of the person and to be able to get married in the not too distant future.
Otherwise what good does that do? Dating around and a prolonged "going together" or however you want to call it without a commitment to the other person is just setting yourself up for problems and pain in the end, especially for people that have a harder time constraining their feelings and emotions that it will bring up.
And then it should be a courtship with the intend to make a commitment that will lead to marriage not just hit and miss dating, trying out, testing the merchandise, see if it fits whatever is in people's minds about this topic which is worldly and should not be practiced by real Christians! Something like that should be prayerfully considered on both sides! Ask for wisdom, God gives it, just ask!