Yoyos to use:
A dedicated offstring yoyo will be helpful. I would recommend the yyf Flight because of its durability.
It is easier to bind the yoyo with a responsive gap width (the Flight is a little bit wide), but with two extra wraps around the bearing, an unresponsive yoyo will bind. You can also use a slim bearing to decrease the gap.
Maintenance:
The lube tradeoff is generally thin gap width and thin lube in order to make the yoyo spin longer.
If you have a yoyo with a standard (M4) axle and you yoyo over anything but grass and carpet, you may want to get a pack of replacement axles off amazon.
Tricks:
The basic throw is a forward pass, and you land it almost exactly like a trapeze.
If you are working on your binds, you may want to replace your strings and response pads more often.
Everything else can be learned from the yyt youtube playlist.
Substyles:
4A allows for the use of multiple yoyos, so a 2 yoyo style similar to diabolos has been invented called soloham.
The best tutorial so far can be found here. Keep in mind that the rhythm is difficult and the tricks are harder than basic offstring.
Transportation:
Dedicated 4A yoyos don’t fit in a standard case. The best case so far, the yyt 5 styles case, can fit 2 offstring yoyos.
Grinds:
If you are desperate to learn all of your grinds, but you still want to play cheap, I recommend the yyt spire. There is a thumb grind lip, bead blasted finger grinds, and a very tight locking finger spin cup.
You might want to look at the yyf tutorials now, not just yyt.
Scoring (2023):
Tricks where the yoyo does not leave the string are not scored. Somersault (Sun) and 360 “slackicide” are not scored. This is one of the reasons that soloham scores low (the others being that binds take forever and there’s low trick diversity).