Ruby has to my knowledge, 3 primary ways of using a Database. Rails is famous for using ActiveRecord, but ActiveRecord can be used independently of Rails. Its well worth learning as it makes database use very easy indeed.
Another Ruby framework Nitro uses a database layer called Og (ObjectGraph) which I presume (not sure) can be used externally to Nitro.
Lastly theres the default, DBI. This is a more conventional database access library, where you are kept pretty close to the SQL mechanisms.
I'd say using rails is a bit of overkill, and you seem to have come to this conclusion as well. i'd also go so far as to say that using activerecord would be overkill for something simple like your menu. you most likely would never use the things that make activerecord beneficial.
if you want something more lightweight than activerecord, check out DBI, which was suggested previously. as far as the actual database goes, you might want to take a look at sqlite3 as opposed to something like mysql/postgresql/etc.
see the first link i sent, that has the installation instructions for ruby-dbi
http://ruby-dbi.rubyforge.org/
if you are on shared hosting, then your provider may already have dbi installed. you'd have to talk to them to know for sure (or write a test script).
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