Tips to play Rubick

Rubick  is a very situational hero, pubs give this hero such a terrible rep and winrate because they pick him every game cuz "he is so versatile he can steal all enemy spells". Nope. Rubick is a pretty poor support in the laning phase, and just because you have Rubick and a hard carry in a lane doesn't mean anything, that kind of lane will get crapped on by basically anything. Now, if your enemy has great spells to steal, you need to position well stay away from the fight and Spell Steal them then. Also, try to lift the enemy right after they cast that big spell, so they cannot cast anything else that might ruin your  Spell Steal. It takes some practice, but lift has zero cast time, so use that to your advantage.

Don't feel the need to go for BIGPLAYS in a teamfight

Often stealing a simple stun or a mobility spell (Blink, Shukuchi, etc) is good enough - if you can instagib a key support or lock down the enemy carry for 3-4 seconds with a Telekinesis and a followup stun, you've probably done a lot for your team.

Try always have a spell stolen before a fight breaks out

If you don't have to worry about stealing something mid-fight, it'll help you pay more attention to your positioning/spellcasting.

Go into every teamfight with a plan, especially when there are big spells on the enemy team to steal

Try to understand who you want to use certain spells on and what to steal, and position yourself accordingly. For example, if you're trying to Spell Steal Ravage, it's sometimes necesary to be a screen away from your teammates waiting for tide to blink in.

Don't be afraid to play greedy, even as a 5 position support!

Spell Steal a farming spell and go farm your jungle. TP into a free lane when your carry is in a different lane accomplishing nothing. Hell ask your team for some space to farm a Blink Dagger. The first mobility item you get is a pretty big deal for Rubick, and if you're not getting it by ~20 minutes tops, something is very wrong with your early-game play.

Analyze each of the opponent's heroes at the start of the game

Decide which spells would be good to  Spell Steal, which spells can chain into each other, which spells suck, which spells you would want to hold onto for a long period. This needs to happen before you even start hitting creeps, so that you can adjust your playstyle accordingly.

As per above, if you steal strong nukes with short cooldowns, hold on to those and gank actively

If you Spell Steal a strong ulti like Ravage, use it wisely, then it is up to you whether you wish to overwrite it with a nuke with short cooldown, or wait for the ulti to cooldown again.

Stay back in fights

Try and predict when key spells will be thrown, and keep your cursor over those heroes to immediately steal said spells when cast (e.g. Shadow Shaman's wards, Lich's  Chain Frost, Pudge's Meat Hook). In doing so, it allows you to insta- Spell Steal. But keep in mind your positioning. Dying in the process of trying to steal a spell is not worth it (especially trying to Spell Steal that glorious Meat Hook). This comes with practice.

You do NOT need to always Spell Steal ultimates

Of course certain AOE ultis such as Ravage / Black Hole can be teamfight-turning (and you can have your own WoDota / DotaCinema moment), but other spells can be incredibly useful as well and waiting for the perfect time to Spell Steal that Ravage when you could have stolen Fissure to stun 3 fleeing heroes would not be that wise.

Rubick has 0 cast time for his spells

Abuse the shit out of this. Fissure,  Split Earth, Ice Path,  Meat Hook, Torrent are lovely spells to steal.

You can chain certain skillshot spells yourself, allowing for easy set-ups / follow-ups

Lift into  Split Earth / Torrent  / Fissure/  Ice Path etc.

Telekinesis + Fade Bolt costs 270 mana in total

Always keep this in mind, and check the cost of your stolen spell as well.
Familiarize yourself with all the icons of various heroes' spells so that in the heat of the battle, you know exactly what spell you stole w/o hovering over that spell.

Usually, the 'combo' goes like Lift --> Bolt --> Stolen Spell --> Steal --> Stolen Spell 2

Should be enough to kill most heroes (depends on what spells you stole). Keep in mind the mana costs required.

Try and hit level 6 ASAP

I tend to struggle with this too; rotation, finding ganks and pulling / stacking would help. Once you hit 6, your ability to contribute to ganks / counterganks skyrockets.

Keep TPs with you at all times

The awesome thing with Rubick is that the opponent does not always know what spell you have stolen when you TP in to countergank / gank, so there is always that element of surprise.

If you steal Morphling's Morph, you can morph Str to Agi and vice versa

Morphed attributes will stay on you permanently, even after you lose the spell. But remember, never go full agi.

Blink into Telekinesis

Blink into Telekinesis is an insane initiation due to its almost instant cast time, leaving the opponent no time to react. Chain a stolen stun on top of that for ez kills.

Item-wise, the usual support stuff such as wards, courier

Hold on to Town Portal Scroll and Smoke. Get a value Magic Stick. Urn of Shadows --> Arcane Boots --> Blink Dagger --> Force Staff. Of course, if you can get a fast Blink, go for it. Urn suits his aggresive gank-oriented playstyle, and Arcane Boots to sustain his high mana consumption. Blink and Force Staff for mobility and positioning. Anything else is luxury.