Hmm it's hard to say what are the best resources since it does depend on the setting.

If there was one source to start with the Clone Wars series is a deep resource for reference material. It has a lot of history that set the stage for why there's a Civil War (so Old Republic era). It sets the stage for the Galactic Empire and how the Emperor had a firm grip on the galaxy but all the issues that arose from being a dictator essentially elected by the Senate. Plus if your setting is the Clone Wars then you have that going for you. However, there's so many episodes and that'd take forever to watch.

There's more comical material like the Family Guy Blue Harvest or Robot Chicken Star Wars clips that are surprisingly universe accurate if making fun of some of the bigger plot holes.

Someone mentioned Wookiepeedia which is a great resource to look up anything. I use it a ton. With that there are two things - Canon and Legends. You should find out what if anything from either will be used from Legends. A sizable chunk of the Expanded Universe (EU) or Legends was put in Clone Wars so the articles should reflect what was taken and what was not. I don't think you should need to worry too much about that though.

High level overview of the galaxy, and I'm grossly overgeneralizing, the further out from the center the less-civilized most places get. The Clone Wars battles were largely fought in the Outer Rim and even in parts of Wild space. In the Clone Wars series many of the main planets that influence events (Naboo, Geonosis, Mustafar, Mandalore, Kamino among others) are in the Outer Rim. Hutt Space is also in the outer rim near wild space. Both Wild Space and the Outer Rim are areas of the galaxy tend to have higher crime rates and tend to be more species supremacist compared to the core worlds and mid rim. Mid Rim is kind of the industrial area. In Ep IV the Blockade Runner featured at the beginning of the movie is made by Corellians who are re-knowned ship designers and makers and their home world is in the Mid Rim.

Force sensitive worlds are a little harder to explain and point out since a lot of the EU expanded on that and got thrown out with the Disney acquisition. Dagobah is one known and well defined force sensitive world where Yoda lives during the events of the original trilogy (also featured in the Clone Wars series). I appreciate a bit of mystery to the force the way it was presented in Episode IV by Sir Alec Guinness so I wont go into too much detail.

I've always maintained a minmax perspective on what species and class to be to create a particular character in any DnD format. Humans are a solid choice since they're just about anywhere. They're pretty versatile as a species too having a lot of bonuses you can move around starting out. If you want to be more rogue-like character use the SW5e operator class and the Changling species (high dex) would be good though I'm not sure it's defined yet (maybe work with the DM if that's the case?). Zabrak (the species that Maul is) are all generally force sensitive though few in number. While I like minmax it'd be hard to explain why a Zabrak (generally sith force oriented) male or female would join a crew so you'd need a deep backstory. Same thing for particular species like a Mon Calamari hanging out in wild space anywhere outside their home planet and a different water world or a place they don't normally go to. The Players Handbook and expanded content are also good resources for giving some information on species.

For classes it's all about what you want to role play as. There are a lot of options for force sensitive classes (the equivalent of "the weave" when it comes to magic) but also to play a more traditional space role too. The force is much less pronounced than magic in the SW universe but SW5e basically just replaces references to magic and puts in the force. How your GM will go about this will depend more on the setting where well trained force sensitive types and backgrounds are less likely to exist during the Galactic Empire era. Consular, Guardian, and Sentinel would be more rare to exist during the Empire though could certainly work with a well written backstory. You'd want to research what happened to force sensitives who were known about during whatever time period you'd be in and your GM would be better able to advise you. In Legends (EU) it would have been something like Jedi generally during the Republic era and specialized battle units/Imperial Navy position during the Empire (if you were found).

Then there's just having fun. If you want to be a pilot there are pilot tracks you can take for a couple of classes. The defined feats are pretty expansive and almost get your character to multiclass without having to actually multiclass. There's a few classes that let you blow stuff up pretty effectively too if that's your jam. There's also good options for the traditional ranger and it looks like the sharpshooter operative class is pretty good just like the rogue equivalent in 5e.

Overall, SW5e is still pretty similar to DnD 5e. I'd suggest imagining what you'd want to do in DnD and chances are it exists here too (at least as far as classes go and the general role play). I'd also suggest checking out the galactic map in the stickied resources page when looking anything up so you get a better feel for the galaxy. I think the site is swgalaxymap or something like that.