you do not say what you are using in the bobbin??? often using the same threads top & bottom help with tension problems- if your top thread is showing on the bottom the top tension is too loose- if tightening the top tension does not get your tensions equal you can try to loosen the bobbin tension a little bit- but i always hesitate to mess with the bobbin tension- it does depend on what you are using though-
also, if you visit the Superior thread website they have lots of great help-tutorials-problem solving ---and you can contact them for (personal) help too.