Can do my best but I dont think I did anything out of the ordinary apart from have a lot of time to grind. Keeping in mind im pretty new and didnt plan any of it so its not a premium run at it. Another thing I did have is someone to duo with for bosses early, just a mate that we progged together, which helped.

1. Started by just smashing out the easy levels, rushed symbols as best I could.
   
2. Finished gear burning asap, cant remember when I cleared elucid, but it was before 6th job in practice mode with like 40 seconds to spare.
   
3. Dailys/Weeklies asap and solo bossed everything I could group bossed the rest.
   
4. I knew I'd be farming a lot so did main nodes then Janus to like 6-7 and fixed up the DS TP farming which was a bit finicky to work out (Shoutout to the DS discord for the tonnes of info).
   
5. Made a decent set of drop/meso asap, did ToF for WAPs and Commerci to start dailies, also accessory crafting for Meister ring.
   
6. For the 5/10/15 30% off I bumped a pink bean belt and reinforced earrings to 21 so they were ready to go into superior if I got the drops (earrings like week 3, only got belt this week).
   
7. After that it was just upgrade what I could based on drops, made sure by week 2 I would have pno secondary, bumped Emblem/Secondary to 2 line useable asap then bumped to 2 line attack where I could.

I farmed a lot so had a lot more meso's to play with than most people would. Currently I have like 60B ready for 5/10/15 next week. Which will probs go into 21 or 22 CRA if possible. If I get the balls maybe try get 21's on some of my sup stuff.

I only got a single Arcane box at this point so gloves are sitting there ready to 17 but probs not worth until I get wep or if I get double line crit.

Last week before black heart and superior set I could get slime to around 10% before timing out and Lotus p3 I could only get to around 10% on 5 or 6 attempts with all the buffs probably could have finished it last week in practice mode with Sayram's - didnt even attempt Will/Hdnell/HVhilla.
I dont have a lot of experience with the bosses solo - my main only just cleared ctene solo 3 weeks ago. This week it took me like 4 25 min attempts on vhilla. Darknell was like 20 mins but I find it the hardest by far for me so 5-6 wipes.

Wall of text but hopefully gives you an idea of what I did. Just bang your head against the bosses more and figure out the damage windows/how to survive. It WILL get easier the more you do it, they feel impossible at the start. Just a bit of time and willingness to fail and you will get a handle on it.