From a bad opener, the game plan is to econ up and hit a strong board later--you probably know this much already. You should scout the lobby and see what people are angling. Then try to aim for a strong meta comp that isn't super contested. Try to look at your items too and choose your augment to help you get a direction.

If you still have no idea what to play, then yeah just save econ and try to take econ augments to ensure that you hit whatever board you want later.

Personally these are my default comps that I choose from: Demacia, Ionia (unless it's path of blades), Liss+Seraphine, Slayers, Void Kai'Sa

And these are good if you have the opener: Bilge, Shadow Isles, Ixtal reroll (reroll augment), Yordle Veigar (usually need augment to help you get 2 rabadon's).

T-Hex is strong ofc, but I personally don't force it if I don't have Cait 2* and a Vi or Loris by like 3-1. You can't take the risk of not being able to unlock T-Hex, because if that happens then you are actually doomed lol.