Due to the flexibility of the GF/Magic Junction system, base battle statistics are rather insignificant in Final Fantasy VIII and, save very few exceptions, have no real meaning (after all, they are almost completely customizable). Still, for mere reference, the following table covers Selphie's different unjunctioned stats every ten levels.
...And, well, because the information is probably useless without something to compare it to, here are everyone's Level 100 base battle statistics (yes, I realize Seifer, Edea and Laguna count as playable as well, but no, I didn't include them, because it's not like you'd ever have to seriously ponder whether to place them in your party):
Now that we actually have something to analyze, it can be said that Selphie's Luck, Speed, Spirit and Magic stats are among the highest; on the other hand, her HP, Strength and Vitality are not too showy. This would make her more of a magic caster than a physical fighter by default (which makes sense, if you take her Limit Break into consideration); however, strangely enough, that's practically the opposite of what I used her for, and I was still very satisfied with her performance (yay for the junction system!). For deeper reflection on Selphie's usefulness in battle (or lack thereof), go here.