>>7367211- G-Generation are the old super-squashy looking SD kits. They're quite small and cheap. Designs are really cute, but they can be a pain because they're made on a very small budget and color separation can be terrible. Articulation is also bad because they're so basic.
- BB Senshi is mostly a nice line. Pretty good engineering that improved a lot over time, pretty good color separation too. The early ones are obviously a bit dated now, but later stuff like the Sazabi and Hi-Nu are phenomenal.
- Sangokuden (ie, the elaborate armored Romance of the Three Kingdoms) kits are usually well-made, but require a TON of painting to look good. There are a lot of tiny details and the color separation just can't keep up. I would avoid these unless you're prepared to paint, they look like shit with just the stickers.
- Legend BB is probably my favorite SD series. A lot of them have damn near perfect color separation, good articulation, they come with a ton of accessories and option parts, and every kit has at least one chromed part. These are a good way to get back in IMO (pic related, Command Gundam in particular is awesome).
- Stay the fuck away from EX Standard. These kits are horrible and everyone hated them. Super cheaply made, lots of hollow pieces, fuck-awful color separation, it's a mess.
- The newest line is Cross Silhouette. The gimmick is that there are two different internal frames you can use to change the proportions of any kit. You just pop the armor pieces onto the frame of your choice, and you can have a shorty or a tall boy. This is a fantastic line too, with very good color separation, and the tall frame has probably the best articulation SDs have ever had. This is also an excellent starting point.
Sorry for the long ramble. I really, really love SDs.