How to be pure strength

First step:
Making you character
Make your character and give it a cool name.  Finish tutorial with all stats at 1.

Second step:
Gathering supplies
Run to goblin house (across the bridge from lumbridge).  Fill you inventory with bones and run to the grand exchange.  Sell all of your bones and it should come to a total of 2.8k.  Use that money and purchase iron full helm, iron platebody, iron platelegs, iron scimitar, leather boots, leather gloves, steel scimitar, mithril scimitar, adamant scimitar, rune scimitar, and a colored cape.  Note: If you start doing the demonslayer quest you can obtain the weapon silverlight.  This sword has equivilant stats to a steel sword.

Third step:
Note:  Since you get str xp depending on how high you hit, it's best to train with str potions.
Strength level 1~20
Start running back to lumbridge and on the way you should see a chicken coop.  Kill chickens and gain profit from feathers.
strength level 21~30
Note: at this point you should be starting to train attack.  Once you have achieved 30 str train attack to 20.   
Cows,  one of my favorite training monsters because of high hp for there level.
Strength level 31~50
Note: After getting 50 str train attack to 40.
Barbarians and guards. Be sure to bring food for both.
Strength level 51~70
Moss giants.  Bring food. 
Strength level 71~80
Lesser demons.
Stength level 81~90
Greater demons
Strength level 91~99
Hellhounds and revenants.