Right starting from the bottom up;
The original sponges that come with the filter, one course, one medium.
Next tray, Bio-media, ceramic rings. I replaced all these with Seachem Matrix(bio-media). This is optional. Topped with the sponge that comes with it.
Next tray, bio-balls and sponge. Again I replaced the bio-balls with Seachem Matrix(bio-media). This is also optional.
Top tray, a full tray of filter floss(100% polyfil).
Finally on top of the floss, I put a 100ml bag of Seachem Purigen. Personally I use two bags of Purigen. As Purigen is rechargeable, I use two, so it is longer between recharging.
The Matrix is completely optional, the original bio-media is completely fine and will do the job. I read great reports about the Matrix, so I opted to use it. The Matrix you want to use is the bio-media version, they basically look like small stones. There is another Matrix available called Matrix Carbon. I'm sure you know the difference, so no need to use this. I had this set-up on a fully stocked 55g tank, including, Platies, Mollies, Guppies, Tetras, and a pair of Kribs. Most of these fish have high Bio-loads and my water is crystal clear. With you having two of these filters, you will be well covered for the fish you want. If I didn't explain anything properly and you need any more info, just let me know....
PS... If you decide to go with the Matrix, I would use it from the start, so you don't have to replace the other bio-media and risk loosing some BB...