It should be emphasized that complex and expensive modifications are not needed to start IPSC shooting. Changes and modifications can always be made as you need them. Don't let yourself get caught up by the current fads and fashion. Competitors may enter any one of five Divisions depending on the style of firearm they use.
Nothing is as important as reliability.
If the handgun functions correctly with your ammo then all is well. If not, your first concern is to make the handgun reliable. Modifications which improve accuracy are good sights and a good trigger. Modifications which increase comfort, control, handling, and speed are items like beavertails, extended magazine releases, checkering, extended thumb safeties, oversized magazine wells, etc. The holster must cover the trigger and should allow the second finger to be placed on the stock when the shooter grasps the pistol as part of the draw.