Hi Elros,
If you're just playing this game again after a long time off, you might not know about the changes with Optimal Rank / Optimal Class for all Items. Essentially, if you're not wearing Optimal Class / Rank Gear, you don't gain any of the bonuses they normally impart.
Some things to consider:
* Are you using a Rank-appropriate Tool? Using only the Weathered Tool (Rank 1) may be a reason you're struggling now.
* Are you using Optimal Rank / Class Crafting Gear? This helps, especially since 1.19 where Yoshida-san has made Stats matter more.
* Is any of your gear that is appropriate damaged? If it's in Yellow / Red, you should repair it.
* Lastly, to answer your question about the colors, White Orb is a safe time to use Standard Synthesis on for sure. If you get Flashing, you should consider "Wait"ing and seeing if you can get something safer.
* You should also equip Crafting Abilities that can help you.
Good luck.
