This may be slightly multifaceted because I have a larger question regarding で that is contextualized by a smaller one.
It is improper to put で before です or だ right. If someone asks 何で来ましたか (How did you get here?) you could reply バスで来ました。 But you can't write バスでです... right? Is there a way to answer without a verb?
Ok that's my contextual question... so my real question is, if it is true you cannot place で before です in this manner, how is it possible to say 初めてです if that is the 連用形 + で.
Or is it a completely different thing all together and just considered an adverb?
SUMMARY: 1/ Can you place で before です per example: バス ＋ で ＋ で ＋ あります. 2/ If not... how is it possible to say 初めてです, as to me that is 初め ＋ で ＋で + あります