OK, here we go, finally.
324 AD: Contact Rome. No deals to be made just yet. Move workers to food bonus tiles and start irrigating. Send curraghs and raiders exploring to at least get most of our tiles in view.
Build orders are a tough call. I think we need to get moving soon enough that the payback horizon for granaries is too far in the future, especially with a food bonus tile already at each city and the fact that we don't have despotism tile restrictions. I order mostly migrants in Ireland. No idea what to build in England; I go with a spearman in the capital and an extra curragh in the eastern city.
Research set to max on Alphabet.
326 AD: Rome traded our contact to East Rome, but nobody else. No sense in paying through the nose for a couple of barb contacts yet.
328 AD: Two turns into the scenario and both Londonium and Eboracum have grown in size
330 AD: We got contact with the Visigoths, and our curragh finds the Franks. We also buy the Ostrogoth contact cheap, for the map plus 20g to Rome.
The Visigoths lack Sailing but have Masonry - we trade. We also sell Sailing to the Ostrogoths for 50g.
334 AD: Too late I realize that what I should've done was have the granary-equipped cities in England build migrants and use a curragh to ship them over to Ireland. Our curraghs have now all left the area.

One found the Anglo-Saxons though.
Hey, worker time to clear forests is the PTW standard 10 turns (reduced to 7 cause we're industrious), not the C3C standard of 5 turns. Several of the Conquests scenarios were obviously made from earlier versions of the standard .bic...
338 AD: Pay 49g + 7/turn to East Rome to finish off our Alphabet research. I do this because we can resell it to the Franks for 64 gold. Start research on Mathematics.
342 AD: We have contact with the Sassanids and Huns, and WM + 4g to the Sassanids gets us contact with the Vandals. That's all of 'em. The Huns have a monopoly on Marauding

but there isn't anything we can do about that (except hope to get Mathematics to trade for it.) I decide to can the research on Mathematics and accumulate cash looking to buy and two-fer.
344 AD: Marauding got traded around. Mathematics didn't. Here goes. I turn almost every citizen into a taxman.
We can pay 44 + 21/turn to the Sassanids for
Mathematics.
Resell Mathematics to Ostrogoths for
Horseback Riding + 40 gold.
Resell Mathematics plus 39g + 5/turn to Vandals for
Marauding. (They wanted significantly less gold than everyone else. Likely they still lack a couple contacts.)
Resell Mathematics to Franks for 84 gold.
Research is now officially off for quite some time, as we've got all the techs we need. After firing the taxmen and going back to 10% lux tax, we're at 89 gold and -14/turn. I do apologize for the economic pickle, but we'll pull out of it eventually, and don't forget to make 8-10 gold each turn by selling our curraghs' maps to the Romes and Sassanids,