There's the stage that people perform on, and the stage that is similar in meaning to rung, level, etc.
The stage where plays and concerts take place is a בָּמָה (bah-MAH). Likewise, a director of a show, or a film for that matter, is a בַּמַּאִי (bah-MAH-ee). The plural is בָּמוֹת (bah-MOHT).
A stage, as in "We have arrived at the final stage of the plan," is שָׁלָב (shah-LAHV). Like many nouns in many languages, this abstract idea of a chronological stage actually comes from a much more concrete word: the rung of a ladder. The plural is שְׁלָבִים (shlah-VEEM).
The sentence above, "We have arrived..." is הִגַּעְנוּ לַשָּׁלָב הָאַחֲרוֹן שֶׁל הַתָּכְנִית (hee-GAH-noo lah-shah-LAHV hah-ah-khah-ROHN shel hah-tokh-NEET).
A level, however - as in, "Ulpan La-Inyan has five fun-filled, highly-effective levels of conversational Hebrew classes to choose from" - is רָמָה (rah-MAH), like the flagship camp of the Conservative movement. The plural is רָמוֹת (rah-MOHT).