For me, the best Aikido mods are Greykido>Aikido>ABD. Greykido has the pads which are always extremely useful, especially when dealing with shovels and lifts and also has the smaller dojo which makes gameplay more exciting. Same with Aikido's dojo. ABD has the big dojo, as suggested by the name, which makes matches slower paced, along with annoying scenarios like having a lack of a grab, so both players have to resort to playing ABD like a striking mod.
In order to get better, you have to play against or watch people who are better than you. Pay attention to joint combinations and ways they counter things. Free play/Singleplayer is also a great place to learn what each joint does, if you don't already have that knowledge and is also a great way to test moves. For example, you could have Uke do a shovel against you and you can attempt to figure out good ways to counter it.