Legalistic or not

To answer the question, 'Yes' I do believe it would be legalistic, by matter of focus. To try to self determine our 'spiritual gift' would be self centered, not God centered and as one poster already stated it would foster pride.
Our goal and occupation is always to glorify Him in all we do. This is not done by deciding what we should be doing or thinking or by self analyzing but by total focus on Him, His ways, His word, His thoughts!
'But without faith it is impossible to please Him; for he that cometh to God must believe that He is and that He is a rewarder of them that dilligently seek Him.' Heb 11:6
This shows that we ever seek Him, be preoccupied with Him, seek Him, believe Him, abide in HIm, communicate with Him.
The spiritual gift would be lived out of our life then as a byproduct of a heart so occupied with God there is room for none else.
Whatsoever we do in word or deed do all to the glory of God'. Col 3 : 17
'Let this mind be in you which was also in Christ Jesus:.....Phil 2 : 5
'And finally, brethren, whatsoever things are true, whatsoever things are honens, whatsoever things are just, whatsoever things are pure, whatsoever things are lovely, whatsoever things are of good report; if there be any virtue, and if there be any praise, think on these things.Phil 4:8