To be honest, you're in quite the dilemma.
The easiest way for someone like you to gain some 6* is by obtaining TE and participate in events as harder as possible. Attempt to get the easier rewards and sell all gods at a potion per set. Once you have ten potions/TE, focus on key 6*, starting with cheap ones then going for more diverse targets.
Several NeoArtCore 7*s are now cheaper thanks to the Challenger Packs that increased their numbers. Finding one for 200 TE or a bit more(cheaper if with pots) shouldn't be difficult.
Just remember, pateince and strategic grinds are the key. Invest, then rest. Invest, then rest. The road is long, but you'll reach it.
For some motivation: i took a full year to obtain a rare 7* from my dream card list that costs more than 800 TE, and i only spent sparingly on a few events (around 5 over said year).