ok as far as i know there is no way of knowing if a support gem is actually supporting a skill as not all support gems work with every skill, so i have 2 ideas.

1. when you socket a support gem with a skill, IF the skill is gaining the support gems abilities, have a very slight energy stream going from the support gem to any skill gems that are being supported in an item, so you can visually see an effect saying "yes your AOE increase support gem is working with your fireball skill gem".

2. i dont know if this is already in affect or already planned but if its not, when you hover over your skill gem and you see its information, there should be sub sets that you can see, that tell you which support gems are effecting this current skill with the exact changes its giving it, not just the general ability its giving, so if you hover over your fireball skill and its linked to an AOE increase support gem, it tells you the exact amount the fireballs AOE increase is.

im sure a lot of people have already thought of the 2nd idea i have here but what do people think of the 1st one, where you get an instant visual on whats working with what skill?