Most Helpful Girl
I recommend you getting items that has a touch of an emo-ish look but that aren't full out emo. Since you know that you parents will not like it and I'm assuming, you still live under their roof.
I do not know where you could get cheap emo clothes but I know where you could get cheap clothes... thrift stores, the downside is that you would have to dig threw a lot of junk but it is worth it!
My last piece of advice: When shopping for clothes, do not look for clothes that represent emo but that represents you.