Okay like, this deck is kinda awful before sideboarding except on the draw you can ramp so uncontrollably it might not matter. Also if you surprise them with hero and suddenly go aggro on turn 3/4/5 when they think you're supposed to be ramping they can get so beat up that it won't take much to pull out a game 1 win. Basically you do the normal simic mana base ramp garbage and if you play against aggro you want to cast uro probably and if you play against combo decks/control you probably want to play tef.

some stuff you do to win: flourish and swing with your tokens like some janky castle embereth pump. in case it's not clear this is actually a mid range deck where the win con is out-ramping your opponent and going wide before they get answers. It's worth it to be aggressively attacking with uro/krasis/hero tokens.

VS. control/combo: Don't fall into the trap of trying to resolve hero to just resolve it - if you're going to go wide you need to have mana to hold up counterspells vs. board wipes, if you don't you might as well just krasis for advantage. your biggest advantage with hero is that if you cast a spell you'll trigger hero for board advantage so there's only 2 things that can stop you - hero not coming down or a board wipe.

VS. aggro: you want to resolve hero asap so you have an endless stream of chump blockers while you're in the process of ramping basically. basically you're racing to a world where you're untouchable even if embercleave resolves

VS. oven: your creatures are incredibly weak to claim but even with mayhem devil pings if you resolve march with hero tokens your board will be so incredibly wide they don't have a chance - this matchup is really really weird, it's about initiative for sure. You can have a transformative post-sideboard game where you replace your low cost ramp spells and some krasis/uros with decrees/knights of autumns/gusts/etc and wall them until you have a ton of tokens and cast march.

THOUGHTS ON CHANGES: chulane might be a real card, nissa might be good anyway, castle vantress/garenbrig might be good, blast zone might be good. brazen borrower might not be horrid. maybe a good high rather than go wide sideboard could be kinda funny where you board out the selesnya token suite with finale/end-raze forerunners/maybe even trawler. i really wanted to play join shields but it'll only be good as a 1-turn combo in the grindiest of games.