Riki - Stealth

Introduction

Welcome to this Riki (Stealth Assassin) guide. I have played over 130 games on Dota 2 till now and I have played in around 120 of them using this hero.
I am very sad to see people just simply assuming that people who play this hero are noobs, this is most certainly not true. At least in my case.
Enough about the introduction, lets get to the meat of stuff!

Early game

the first few minutes of the game can actually make or break your mid-game when using this hero. You must, I mean you must be the first one to hit level 6 in the game to dominate in the mid-game. To do so an impeccable start is necessary.
So, first of all as you can see from my "starting items" and my hero "skill build"
I am using the entire 625 gold and putting the first skill in Permanent Invisibilty.
Use this to your advantage, go get one rune stay (stay just where the runes will spawn) and grab it before anyone else. You will not be damaged because you are Invisible so they will not see you. Do not engage the enemy, you WILL DIE.
So after grabbing the first Rune, you now have an advantage in your lane, so farm quickly to get 150 gold in total and immediately buy the Magic Wand to free up your slots so you can buy other items. Have a courier deliver it to you.
This part should preferably be done before 1 minute of the match is up. So this requires great precision and practice.

Between the 2 minute and 8 minute mark

Unless you are playing at a professional level this period for you will be pretty safe unless you act stupidly. Keep farming effectively and build your Power Treads(set active ability as agility obviously) as quickly as possible and hit level 6. I know hitting this within 8 minutes is difficult but if you get all the 4 runes that will be spawning in this time (the permanent invisibility makes this very easy) then you will easy hit level 6 right at the 8 minute mark.
once you hit level 6 you must now take control of your lane. Level up your Ultimate (you should follow my Hero Skill Build) and you will immediately have 4 blink Strikes at hand. Now sneak up behind the enemy (if in dual lane get behind the squishy one) and Backstab him once, then immediatly cast Smoke Screen and strike him again (this time from the front as he will have turned) then continue hitting him till he realizes he will die if he fights you in the smoke screen so he will try to move out of the smoke screen, you will get another Backstab due to this.
By now, the enemy should be down to at least 50% of his base health, he will try to use some ability on you, but before he can do that you Backstab him again by doing a Blink Strike. Now fight him and continuously Blink Strike till he dies. Most of the time (around 90%) you will emerge victorious because he will not have his ultimate at that time. If you are lucky you could even potentially get 2 kills if you have 2 enemy heroes in that lane.
You should get your first kill by the 9th minute or else you will have a horrible mid-game.
But! A horrible mid-game does not mean you could not be useful in the late game. In fact Riki becomes very powerful in the late game so don't worry if you have a bad early game or even a horrible mid game. The End game will make it up.

From the 10th minute to the 25th minute

This period is what I like to call the mid-game. During this period you should focus on farming and getting kills from squishy heroes (like Sniper and Lina).
Don't go after tank heroes like Pudge or Spirit Breaker.
Build the early core items completely and then follow up with the mid-core items.
By the 25th minute you should have everything listed till the mid-core except the Butterfly (if you have that then even better).
The diffusal blade comes in handy by purging Bounty Hunter's Track and Sladar's amplify damage. Both of which make you visible. It also slows down enemy heroes escaping from your smoke screen or those who are running away with 10 health because you ran out of Blink Strikes.
By the 25th minute I usually have over 10 kills and maybe 1 death.( I play in public matches since I have not yet hit level 13 in Dota 2).
Don't worry if you have like 3 kills and 7 deaths, because things regularly turn around in Dota 2 and they usually do after the 30th minute.

From the 30th minute to 45th minute

By this time you should be level 16 to level 20 depending on the type of game you have had, but anything less than level 16 at this time means you are certainly doomed. I mean it would be better if you worked quietly and simply worked like an observer ward and dewarder(removing enemy wards) for the team and generally working a a full fledged support, because you will simply be providing the enemy with free gold and XP since you are so weak.
If you are level 16 to level 17 you have had a poor early and mid game level 18 is pretty standard. Anything above 18 means you have been playing very well. And if that is the case then continue doing what you have been doing till then and build and buy according to my build and you will win the game easily.
Actually, Once All my teammates abandoned the game at around 18 minutes, so I initially for the first few minutes faced a lot of problems as everyone was attacking the towers, but due to the extra gold I was earning I soon put that problem to rest by killing the entire enemy team when they all pushed mid and won that game single handedly after around 30 minutes.
Riki reaches his peak of powers around the 40th minute (around level 23) He can really gank very effectively.
Note by this time you should have the Final 6 items that I have listed in my Item build.

After 50 minutes!

Well after 50 minutes if the game seems to have no end than well, Riki now loses his power very quickly with respect to other heroes. After the one hour mark you must be very careful and should not roam around alone.

Friends And FOES

Friends

Any hero that can stun or can hold an enemy hero in one position (IO and Crystal maiden). These heroes will certainly help you in laning and getting early kills.
FOES

Riki is easily countered by Bounty Hunter's track and Sladar's Amplify Damage.
he is easily countered by Sentry wards and Gem of true sight carrying heroes.
Be careful about this and if you do get the gem by killing the enemy then immediately put it in base. Don't risk it.

End notes

Will be updating this guide soon with appropriate colours and details. Stay tuned.
also fell free to ask anything about the guide you don't understand.