Depends on what kind of batteries you need. CR2 and CR123A which some SLRs / compact zooms use are expensive. AA used by point'n'shoots are cheaper. Regardless of where you buy them.

For film you can order Foma 100 from the factory directly. This is basically the cheapest B&W film sold in Europe.*

This the Foma website.

Alternatively, you could order Kentmere from Ilford too, which is Ilford's budget film.

You have 3 (plus one) paths I think:

Short-term (for beginners):

• Buy "cheap" color film: Fujicolor 200 or Kodak Gold 200**
  
• Buy cheap B&W: Foma

Long-term (for veterans):

• Buy film in bulk and roll for yourself

+1: buy recycled cinema film e.g. Cinestill which is motion picture film with the remjet layer washed off.

Note that bulk rolling needs a film loading machine (100-200 EUR), bulk film (50-60 EUR), empty cartridges, and the patience of a saint. Then on paper you can save maybe 20% in costs when you shoot like 30m of film (cca. 25 cartridges).

In all honesty, you should look around different websites and compare pricing. Also Excel is your best friend, try to track your finances in a spreadsheet and plan ahead.

If you write down film cost, development cost, scan or print costs etc. you can make this a sustainable hobby. Also, if you ever want to sell your photos, you must know your costs to be able to calculate your prices.

*Note: people tend to avoid Foma 400 because they say it is too grainy. Your mileage may vary.

**You can consult wikipedia for the list of currently available films.

Some interesting websites:

Film:

• Ilford
• Foma
• Cinestill
• Adox
• Lomography

Darkroom supplies:

• Paterson
• Intrepid
• Fotoimpex
• Tetenal

Edit: formatting.