I guess the list of "good" divisions is kept on this forum, with all the regulars ready and willing to regurgitate them back at you. Without going over 20w:
Infantry divisions: 10/0 (that is, 10 INF 0 ART) are currently the meta, with 7/2 (7 INF 2 ART) languishing in the background. You could also switch to a 5/0 for coastal garrison work, or knock of an INF for a tank (preferably HARM) for a poor man's offensive division.
Light Tank Divisions will usually be something like 3/4 LARM 4/3 MOT 2 ART. What ART that actually is can wildly vary and one of them may be replaced by extra TD/AA/etc. depending on the circumstances. Light Tanks, however, are typically relegated to support companies, MOT divisions, or conversions such as LSPAA.
Medium Tanks follow the same sort of general outline, though I should probably note that 5/5/0 works just as well against the AI.
The same sort of thing applies to HARM.
Motorized attack... I'd say something like 6 MOT 2 LSPART 1 LARM.
Mechanized works just fine as a replacement for INF - it's typically not worth including LARM in the bit of the MECH division that contributes to CW. Then again it's typically not worth researching MECH either.
For everything else, just follow the two rules: 1) Have a good reason for the CW of your division ("factor of 80" is typically a good one) and 2) The AI is dumb so you can basically make anything work against it (Artillery Only!). Oh, and if I've got anything wrong, I'm sure I'll be quickly corrected.