EARLY TO MID GAME! ★
Early game Aphelios starts off with constant poke and harass with Calibrum auto attacks mixed with aggressive Q's. Being able to out range from level 1 is great for establishing momentum in the lane and helping get an early gold advantage. Very few champs can deal with the early aggression especially when combined with that of an unorthodox AP support eg Lux, Heimerdinger, Brand, Zyra! Alongside your Calibrum is your Severum on offhand, this helps keep you afloat in lane without heavily investing yourself into early Life Steal. Adept usage of this can allow you to overheal and out sustain your opposing ADC quite easily with an early Dorans Blade. Note that when you use Severums Q that you gain a significant movement speed boost, this allows for a great gap close or a disengage too. Early game using Severums Q can allow you to heavily trade while re-gening quite a lot of health in the process. Take advantage of your pressure if you achieve level 2 before the other laner.
Once you hit around level 3 or so you'll become a lot more reliant on your Gravitum. This gun is used purely for kiting, stunning and slowing. Aphelios uses this to disengage from ganks or if he gets caught out in a 1v2 scenario. Combining Gravitum Q with Severum Q can allow you to AoE stun and pull of great combos with your jungler or support. The guns attack speed is significantly lower than that of other weapons but with good reason, each auto attack slows and then stacks are consumed as a stun when Q is used. Using Gravitum stun allows an easy unmissable Calibrum Q!
By level 6 you will be balancing all weapons with Infernum and Crescendum now being available. Infernum is primarily used for clearing massive waves of creeps and procing multiple offhands eg, AoE Calibrum Marks, Multiple Chakrams and AoE Gravitum stuns. Crescendum is exceptionally good when getting caught in melee range as the attack speed can be devastating especially when getting multiple Chakram stacks. Crescendum Q is fantastic for helping take towers/objectives or procing other weapons special effects. Your turret can be an AoE monster with Infernum offhand, a vampire lifesteal Sentry with Severum offhand, a Sniper Elite with Calibrum or a great disengage stun machine with Gravitum!
MID TO LATE GAME! ★
Mid to late game, you've hopefully turned into the hyper carry (we've all seen the videos!) that you're aiming to be. Your damage has the insane potential to one shot the majority of squishies, but - you yourself are also very easy to be assassinated. You must watch your positioning at all times, just like most ADCs. During the mid-game, focus on accumulating as much gold as possible. Based on the outcome of the laning phase, consider working with your team to venture into the enemy jungle. To maximize your chances of farming, try to remain in a lane where you can farm minions solo, typically the mid lane as it provides better protection from enemy ganks. Once you've pushed the wave, join your team to secure vision. This will increase your chances of securing kills and objectives, which will give you the advantage in the game. Keep in mind that in lower to mid-level play, ADCs often overlook the importance of continued farming in the mid and late game to maintain their gold income.
For champions like Aphelios, who scale well with each item, any item advantage can greatly impact their ability to perform in team fights. In this part of the game, try to keep your Gravitum, the Gravity Cannon, ready to engage enemies with your ultimate, Moonlight Vigil.