Linker 1 is better for you as a support but won’t make your grinding life much easier.
Warlock/Necro 1/2 is a viable option for DT/Flesh Cannon, if you want to take something else as rank 8.
Cryo 3 > thauma 2 is not really good overall but for selling purposes you should go either Linker 1 or Warlock 1.
Pole of Agony and JP + HK scrolls will most likely be the most sold ones. Pole of Agony for the reason that it’s useful at level 1, probably a must for Warlocks, JP level 5 scrolls itself can make a huge difference in places like ET for non-meta parties. Both are solid choices for Enchanter, Gust level 1 might get some space in the scroll market too as most enchanters are either Pyro or Wiz 3.
My opinion, to be honest, is that your build is messed up, Every single Thauma 2 in the game will pick Enchanter for Reversi scrolls as Thaumas are doomed at R8. You don’t even need need attributes to use it, it’s a level 1 spell so it’s one of the cheapest.
Cryo 3 > Linker 2 > Warlock > Enchanter would be a nick set probably. Gust level 1, JP level 5, HK level 1, PoA level 1 are scrolls that might be used a lot on 300+ grinding.
The thing is, Reversi scrolls will be sold more, but JP1/5 and PoA are most likely the rarest ones as Linker > Warlock is good sinergy and people won’t abandon their builds for Enchanter sales, meanwhile every Thauma 2 will drop it at R8.
If you still want to play your build, go Warlock and buy JP scrolls with the profit of your sales. Because you can get 2x PoA with attributes making your own scrolls, so you combo it with Frost Pillar once a minute. Use JP scrolls for DT and other sources of damage. With Thauma buffs you can still do fine IF you afford JP scrolls.
That is: If you can’t find grinding/questing/monster counting parties., If you can with Linker 1 your life becomes much cheaper, though you can’t quest alone.