Low-hanging fruit: Double-check the ILS frequency if you’re using auto-tune - the Navblue (built-in) FMS database has some incorrect frequencies. Compare to a published chart like Skyvector, etc.
If freq is okay:
I tend to hit APR as early as 10-15 miles out. The FMS will automatically switch to LOC1 just before or at the FAF if it didn’t before. Just be sure to hit the fixes at the published crossing altitudes, as VNAV is not yet implemented on G3000.