I just did my first labyrinth run with sparky. I should have waited till he was r5, but I used my r4 as I am too impatient but also as I wanted to experience how the original runs went with 4/55 starlords. Now I have compiled a small list of tips that I do not believe are mentioned much for labyrinth, a few of which will pertain mainly to sparky.
1. Take the colossus shortcut only if you have a champ that does not rely a lot on bleed, as he is really long if you use a champion like blade. If you have sparky or starlord then you are golden, but people do forget that he has the same health as maestro.
2. If a fight is going badly, take a break and try to find that fight on youtube to improve and also give yourself time to relax. You will definitely spend far fewer items if you are playing whilst calm.
3. Don't be afraid to take a break. Some people think that you lose a bit of momentum, and many are tempted by the massive runs on youtube, but just take like 5 or 6 fights and then stop. The longer you play for, the less concentrated you become and also your thumbs may get sweaty, which can interrupt gameplay and cause you to attack when you mean to dodge. The result: Death
4. Forget about the evade. If a champ evades and then hits you there is really nothing you can do about it. If you play and just concentrate on getting the opponent down without worrying about the evade then you are far more likely to have a good run. You just have to accept that it may happen and maybe swear at the screen a little

Side note: When playing sparky, I would try to keep the opponent over 1 bar of power. As the AI in labyrinth is so aggressive, it will often evade into a special attack if it has enough power. If you are playing with starky, then you actually have a 2 in 3 chance to evade the special attack automatically.
5. Unstoppable Colossus was a bit annoying for me, so I'd recommend practising just evading him (not hitting him) and see how long you can last. Speaking of our resident punching bag, you should also aim to have at least 100 health potions for the magik and war machine fights, as if you heal to full, the block damage from wm sp1 and limbo will be massively reduced. I, boosted, survived like 20 limbo's in a row from that bimbo at max hp.
Side note: When using spark, wm is actually a relatively easy fight as you are very likely to evade at least some of the bullets from the sp1, and makes it very easy to build poise.
6. Be prepared for antman. I thought it would be super easy, but boy was it long. He was glancing most of my hits, so they didn't crit and so the fight was extremely long. I got tired, slipped up and got slapped up.
7. Always bait venom's sp1. Never the sp2. EVER
Side note: Yes again, another sparky tip - whilst using him you can get 2 poise charges by evading late, but most of the time you will just get 1.
8. Maestro. For me sp1 is not that much of a problem, but if it is just run him with 3 stars on act 4. Actually good for building 2 poise charges and he is nice and aggressive so poise is really easy. HOWEVER. When using a tech champ, he has the chance to gain random buffs. 1 power gain is no problem, even unstoppable you can sometimes deal with. BUT that regen is so bad. Had about 15-20 force quits due to that annoying little green buff. Maybe I just got really unlucky, but be prepared for SALT. Also don't heal up on maestro, as you can be guaranteed that anytime you do, the regen will pop up and you will have to force close. Coincidence...? Hmm
9. Realise that you are attempting labyrinth of legends - its okay to die. Just play at your own pace, no one is going to judge you.
So there it is, my short list of tips for labyrinth of legends; I hope that this was useful. Please feel free to post any additional tips that are not frequently mentioned in the comments to help other summoners complete this challenge