Most OW aboreals are very feisty and fast, all the good "beginner" OW are terrestrial but Taps and psalmos are NW that act very similar to OW but without the venom. As for OW, there will be a good chance that you will run into pokies and C.darlingi or marshalli. The latter two are pretty good starter Ts as they are hardy and generally aren't overtly aggressive. Pokies aren't necessarily defensive but they are very fast so you need to have some preparation with other fast species before you go for them. If money is no option, M.balfouri and H.gabonensis or villosella are all very pretty and more "chill".
Just get the one you want. They all have the same potency.there are three that need cooler temperatures but besides that they are treated the same. I would hold off getting one as your first ow though if you have not had fast ts. I find my p.metallica the most easy to work with out of the three pokies I have. Some people argue ornata is the most temperamental while others disagree so you really can only rely on what individual you get.
I did have a MF P. irminia, is that enough preparation for one? And I've heard that potency does vary slightly and after reading bite reports it seems like P. metallica is on the low end of the pokie spectrum. I imagine I'm wrong though. I'll be sure to post pictures of what I got on here if I get anything. I'm not too concerned about not finding any old worlds I like because I made a list of what I would like to get.
Yeah P.irminia is fine preparation for a beginner OW but not a pokie. The best way to prepare for a pokie is having experience with OW in general, the other species I suggested will work wonderfully because they are less prone to bolt but are still rather fast. Pokies are not going going anywhere so it's best to work your way up to them so you are able to care for them the best you can. Pokies make Psalmos look like turtles, so other OW will prepare you better for defensiveness and speed.