I've got no clue how popular (or familiar) it might be in the USA. But, if you want to alert people to your chosen pronunciation, why not use the French/Dutch version,
Gilles (or
Gillis, which is a bit surnamey) - that extra L in the middle makes it look distinctive. In French it'd be Zheel, but in Dutch and Afrikaans it's more like Chil-us, with that Ch being, as they say, like the -ch in Scottish 'loch'!
If you want to retain the rhymes-with-Miles pronunciation, then why not stick an H in - Ghiles? It looks odd to me, but the sound you prefer would be clearer.