I want to get media software to do advertising

You must ask yourself "what do I need?"  How much do you need to be able to do yourself?  Will you be printing inhouse, or outsourcing?  If you are getting an outside body to print your brochures, can you make use of their graphic designer?  Can you simply supply some text and let them do the rest?  Certainly, some print companies, e.g. Snap Printing or Print Bureau have a design service inhouse.  Or maybe you can contract your own graphic designer to design your publications.  Often a designer will have a preferred printer with whom they work regularly.

If you wish to do the design yourself, then you must make sure that you can output a file at the end of the day that the printer can use.  Typical file formats include high resolution (300DPI+) PDF and JPG.

Microsoft Office includes an application called Publisher which is not something used by professionals, but is simple to use if you are comfortable with any of the other MS Office range as it uses the same standard controls as the rest of that popular suite of applications.  You will want to check with your printer that they are happy to accept designs in Publisher's .pub format.  If not, Publisher will export designs as JPGs.

When creating adverts and features for other people's publications it is sometimes acceptable to run up a rough draft in MS Word (or equivalent) using the included drawing tools and then let the publication's desktop publishing team take care of the actual implementation in their newspaper/magazine.

Finally, if you feel that you intend to do a reasonable amount of design work inhouse and are not afraid to invest some time in exploring a new tool, there are two excellent open source applications available for free which can cover the bulk of your graphics needs.

GIMP is a graphics program akin to Adobe's Photoshop.  It contains a host of features and as it is open source, has many third party extensions and plug-ins to extend its functionality.  GIMP is good for photo editing, doing layouts, creating web graphics, sketching and animation.  It will open and save a plethora of file types.

Inkscape is another graphics program.  It created vector-based images (as opposed to bitmap images like photos) which allows infinite resizing of the image without any loss of quality.  Inkscape would be useful for creating logos, mastheads, banners, blocks of text in various sizes: anything that might need to be resized.  Inkscape works on the standard SVG filetype, and will export PNG bitmaps for insertion into your documents and designs.