Sonic Steel has saved my life several times now, First Strike is a life saver for sure.

Anyways, I made my way through Macalania Forest with a few game overs, but overall without too much trouble. I've been stealing like crazy with Rikku and have gotten some pretty useful items (x3 Silver Hourglasses! I'll be saving those for bosses though). I bought Sonic Steel from O'aka as well as a Blue Armlet for Kimahri (Water Ward).

Spherimorph
~ Tidus, Yuna, Rikku

The battle started with me switching Tidus out for Auron. From there I followed these simple steps:

Yuna - Heal everytime someone is hit.

Rikku - After Auron attacks, use an item with the opposite element of whatever magic Spherimorph countered Auron with (except Ice, I have no fire items for Rikku to use).

Auron - Attack to reveal the Spherimorphs current elemental barrier.

Everytime Spherimorph was weak against fire I switched Yuna out for Lulu, who used her Fire magic (it did about 600 less damage than Rikku's Use command, but it's all I had).

Spherimorph went down in one try, mostly due to the fact the most damage it could do was about 250 - 300.

~

I'm running around Macalania Forest and Thunder Plains stealing useful items with Rikku, unfortunately I rarely encounter Qactuars so gaining Chocobo Feathers (Haste) is taking a ridiculously long time.

EDIT:

Tavrobel: I've found that Chimera's are the least of my worries in the Forest. I steal once with Rikku (Arctic Wind) and then one hit from Wakka's TKO usually finishes them, if not, Lulu's Fatal Cait Sith does. I'm far more afraid of running into two Blue Elements. Watera kills EVERY character in one hit (except Yuna in critical HP, she has SOSNulTide on one of her armors), and I don't want to waste one of the few Silence Grenades I have.