Well, Who would have though that a bunch of keys and scraps would be useful to people. In the Community of TF2, We all plead for unlimited keys so we can unlock crates and use them as money.
'This is where I come in'
I will tell anyone who will bother to read my guide everything I know about gaining keys and metals.

What are they?
When someone talks about keys in TF2, they are talking about Mann Co Crate Keys you can buy for £1.79.They can: unbox crates, buy TF2 items, convert into refined metal and so on.
Refined metal can be crated in the crafting section when you click on the items section at the main menu, this is also used to buy TF2 items.

Brief Description
Refined metal can be crafted using 3 reclaimed metal and 3 reclaimed metal can be crafted using 3 metal scrap the equation is like this:-
3 RM = 3R = 3S
Metal Scrap can be crafted with weapons you can get from drops but the weapons you craft has to be used by the same class for example:-
Apoco-Fists + Tomislav = 1 S
Unfortunately, Keys cannot be crafted meaning you can only buy it in the Community Market or in the TF2 shop.

How can I get numerous of keys and metal?
Okay! This is the most important part so read carefully guys.
To get started as a user who has recently turned into a P2P, she joins on a server and she sees everyone with pretty cosmetics then she gets jealous and suffers depression.
Forget about that Part!

Anyway to get started, you will need metal scrap and to get metal scrap, you need weapons but you don't have a lot of weapons though or you don't want to give them away so... you idle
Yes yes, this may be seen as cheating but in everything the people hosting the server should get the blame so your the least of Value's Worries.
Idle is (in terms of games) when you AFK in an idle server and you have been spawned at a place where you die, however when you die, you will have a chance off getting a weapon that how the weapon drop system works.
*NOTICE whenever you died, it will show a notification of the weapon you found, idling breaks the boundaries and does this continuously. It doesn't give you weapons all the time you have to be patience.
Anyway once you have some weapons craft them and make scrap metal, another easy way to get scraps is selling weapons for scraps ,awkward i know, tell everyone that they can 1 unique weapon for 1 scrap. Okay trade with them blah blah blah and you get your scrap but if you don't have that specific weapon the other person want go on scrap.tf they have every single weapon so you trade an unwanted weapon with the selected weapon trade with them get the weapon trade with that person and get one scrap
*NOTICE Tell the person to wait for you - never let a customer get away.

Second part:-
So you keep on doing that until you get some refined metal 9-10 will the do the trick which brings up to the most tiring part.

Okay you have some metals but you have not reached your goal, you will need something to boost you up and that is .... Killstreak Fabricators
Killstreak Fabricators are items that you use to make a weapon more expensive and add some sheen and effects
They are different types of sheen:
Name Color
Team Shine Red/Blue
Hot Rod Pink
Manndarin Orange
Deadly Daffodil Yellow
Mean Green Bright green
Agonizing Emerald Subdued green
Villainous Violet Purple

Sheen give the weapon a shining effects depending on the name of the sheen and you have Killstreaker.
The effects are:
Cerebral Discharge
Fire Horns
Flames
Hypno-Beam
Incinerator
Singularity
Tornado
Killstreaker is available to Professional Fabricator while the sheen is available to the both of them (Specialized and Professional) and the Killstreak doesn't do anything so yea. The one you are after is Specialized because the it is quite expensive and you don't need a lot of thing for it.Buy the fabricator in backpack.tf , go on trading,click on classified listing and go on filters and make sure the Specialized Killstreak is enabled. Click on the weapon you would think anyone would like such as an Ubersaw or Eyelander.
*Notice Be logical if you don't have the weapon for the fabricator don't buy it. Simple
So you have the fabricator, you can get started to make the kit you need robot parts - this can be obtained in MVM but you don't have time for that so you need to buy it off scrap.tf.
Remember! If you need more refined metal follow the first steps or sell some of your cosmetic- I am probably guessing you have cosmetics by now.
So you got your robot parts and it has all been applied in the fabricator now you need one thing which is a Killstreak weapon to get one you need to go on backpack.tf.
Trading then Classified Listings and then filter (...)

The following things has to be enabled:-
Scout
Soldier
Pyro
Demoman
Engineer
Heavy
Medic
Sniper
Spy
Standard Killstreak
It will give you a listing of the cheap killstreak which you can buy for a low price.

Okay, It has now been applied and everything is done you can apply it on the weapon or sell it on scrap.tf
If you choose the scrap.tf choice you can repeat the process but if you choose apply to weapon. You need to give it away, this can be done in many ways:-
Backpack.tf
Trade Servers
TF2 Outpost
TF2WH
Bazaar.tf

You trade it away and get the loot and you repeat the process, you gain over 5 ref doing this.Once you get 20 ref you can go on Scrap.tf and convert the refined metals into a key.

There one key but to get lot of keys, repeat the process. Don't buy your ref on silly things, focus on the objective. At some point, ask your parents to apply for a debit card for you, they can add money on the card for you to spend on the market and buy keys and crates hoping to get something good.

Please listen to me, doing these steps has got me where I am so don't search up for hacks because they won't work with stupid surveys and passwords that makes you waste your time.

Lots of people, say that they are too scared to ask their parents for money but I was like that too ; if you want something they should allow you to have it because they are supplying their kids and if they aren't convinced show them this guide because this guide is the guide of TF2 and they shouldn't stop if you unless you have SATS or GCSE in the way then you have no place to argue with them.

Please, show your love and commitment towards this guide and like it, comment and most importantly share it to the world I would like that.

Best Regards
SuperSageRodrick