Requested by a friend, not gonna put alot of effort.
First guide
Blah Blah Blah

I run down 21 down in offense taking everything ad-related except crit damage. I feel like Ezreal shouldn't depend on crits. However, If you're lucky, getting a crit is nice once in a while. This will bring out Ezreal's nice damage. For utility I take reduced death, increased experience and increased buff duration.

My personal preference.

Marks = armor pen for Mid-Late game
Quints = two armor pen and one AD for damage throughout the game
Seals = AD for early game
Glyphs = Ad for early game

Using these runes is a risk, but I plan on using Ezreal's mystic shot, which has a decent low-ish mana cost and long range.
However experimentation is nice once in a while...
Try using stuff like HP quints or armor seals and w/e if you feel like he's too squishy
Or try using mana regen if you like to spam ALOT

I like to start with Doran's Blade. good starting item. damage/health/lifesteal

My first B I get boots and/or another Doran's blade (for increased, better laning experience and sustain)

I then procede to a Black Cleaver. Why? Because it shreds armor and gives some AS as well as some sweet damage. Many might think "Why didnt you rush a sheen". I don't think it's needed this early. However my next item is

Sheen - works with Mystic Shot, makes hit like a truck sometimes. I don't go into Trinity yet though... I'll get into it later.

Bloodthirster - Damage + lifesteal = a nice item for a carry. Each kill gives more of these stats too. Also since Ezreal's Q procs on-hit effect, lifesteal also applies. So if you're incapacitated after a fight and yet your team still fights, you can keep shooting your Q to do some damage and heal up.

GUNBLADE - Why? I'm playing an AD EZREAL why should I build a Hybrid Item? First of all I often get bilgewater cutlass first for lifesteal and damage. Then the AP side of it is optional. This whole item is optional imo. However since I think 2/4 of Ezreal's skills are based on Purely AP and 3/4 of his skills deal magic damage, I think using your W and E can be a lifesaver as well as damage dealing skills. So... I thought: "Why not?".

Defensive Item: I prefer GA. This is what you decide though. Personal Tip: QSS is underrated but I Love it so much.

Trinity Force: Finish off the Sheen. Why didnt I get this earlier? I don't find the other two components needed. Hell, I can buy another BF sword with the extra money. This is my last item to finish.

Personal Preference
Flash = Good on everyone

Your E might be on CD
"O**** I GOTTA GET THE HELL OUT OF HERE"
catching that guy over there who has enough health to die from a mystic shot/aa

Exhaust = screw up another carry/ make 1v1 easier/slows

Rammus is rolling to my *** but I exhausted him and everything was K

Other good picks are ghost, ignite, or w/e you feel is good.

Mystic Shot > Essence Flux > Trushot > Arcane Shift

MYSTIC SHOT ALL THE WAY
MAX IT FIRST
SPAM THIS **** TO HELL
REAL AD SKILL FOR EZREAL

Essence Flux - I max this second because it's Ezreal's 2nd semi - spammable skillshot
I often prefer this over Arcane Shift because it can ruin carries like cait/vayne/tryn, and buff an ally's AS for pushing or whatnot. Fast passive stack when a teamfight occurs (other than ult). Another reason I max this over Arcane Shift because the damage from that flash is often luck to hit the guy you WANT to hit. And you shouldnt rely so much on Arcane Shift too..

Arcane Shift - Flash, quick damage. However it hasa lil delay upon casting. I often use this to catch up or for defensive reasons.

Trueshot Barrage - global skillshot that passes through everything.
Short CD, should use it to clear minion waves/steal buffs/ snipe. Always be aware on the map for low health enemies to snipe em with this. ALways worth a try. Also this skill will wreck teamfights. In a 1v1 occasion somehow, blasting this in a oblivious guys' face will deal nice damage.

Not expecting positive comments
Thanks for reading
Have fun
Bye