I never researched 1940 planes as it was only 1939 when I attacked France and such. It was Oct of 1939 and I was just starting to research such planes. As for mediums, I never produced them from the start as I was too busy focusing on arty, planes, support equipment and AA guns. Hard to focus on tanks when arty is expensive. As for mechanized, no.
Seems to me like you're saying I should be researching things way earlier than I am supposed to like 1940 planes in 1938. I dont think I like that and I would like to request a different idea here on why things are going on. If its because im behind on research in 1938/9, then the game is poorly balanced.
I'm not quite sure I understand your meaning when you say "I don't think I like that." Do you mean
1) I don't like it for historical or role playing reasons.
or
2) I don't like it because I feel like I sacrifice too much in other areas by researching ahead of time.
or
3) Something else.
For the very last bit of that quote, the game balance is irrelevant in my opinion. We can't complain about game balance as an excuse for not being able to win when asking for help, we need to make use of the tools we have in the best ways possible under the game systems as they currently work, however that may be. You asked for advice on how to win, and I'm trying to help with that as best I can. You don't have to follow my advice or anyone else's, but you make it much harder for yourself by not researching important technologies ahead of time.
If it's the first option:
There are still some things you can do to improve your odds even without ahead of time research aside from bonuses. For air, even if you don't have 1940 planes unlocked, you should be putting the first 175 air experience you get (from air volunteers in the SCW) into adding level 5 engines to your fighter 1. Upgrading engines as much as possible and making sure that your fighters have the light air designer for extra agility will help you win the air war much more easily. This allocation of experience takes priority over all air doctrines and spirits. Speaking of spirits, you really want to go for industry liasons as quickly as possible to research fighter 2 even faster when you decide to go for them, and centralized control to make your fighters perform better in combat.
For air doctrine, make sure to go for at least the air superiority mission efficiency +20% doctrine, not the ace generation chance doctrine if you're taking battlefield support. Operational Integrity is the best doctrine for fighters upon completion, though it is only marginally better than Strategic Destruction, and slightly worse in some respects since SD gets its all important fighter agility doctrine one doctrine sooner. As Germany you should probably still be going Battlefield Support though, since you have so many discounts and bonuses specific to that doctrine.
If it's the second option:
The most optimal way to win the air war is to start researching 1940 planes as soon as you can afford to without missing out on too much other stuff. It's entirely possible to put a research slot on them as early as 1936, though not needed in single player. There was
another thread on when to research fighter 2 as Germany recently, with a lot of good comments by experienced players, I'd check it out if you want help on that front. But my preferred strategy is to research fighter 2 starting in mid 1937 after all the key industry techs are done or on other slots.
I don't bother keeping up with infantry equipment technology at all. Counterintuitively, researching them is kind of a pitfall. Infantry as Germany mainly exist to hold the line, not to attack. Attacking is best left to tank divisions which Germany excels with. It's not a good idea to invest a lot of research into something that's only there to stop you from losing, you want to invest into weapons that will win you the war. You do need artillery research both for modern support artillery and for unlocking medium howitzers to put on your tanks, but you don't need infantry weapons or infantry support technology to beat France or even the USSR.
Germany gets so many bonuses to tanks that you can easily have a fully upgraded 1940 medium tank in production in 1937 or 8. Use the close support gun in single player until you unlock medium howitzers since it's cheap, you start with it, and it has very high soft attack which is king in single player.
And my only tank designs were what was given from the start. I didn't have the army exp as im focused on my infantry to actually do anything.
This is a big problem. You have mobile warfare doctrine, you can take the army spirit to make designing tank templates free for 35 xp. You also only need to spend about 30 xp to design a good tank completely from scratch. You should be getting hundreds of army experience from volunteers to the Spanish Civil War, from your chief of staff and army high command, and from any lend-leased guns you sent to Spain. It should never be a problem to design a tank.
The prioritization of army experience should be: spirits -> tank designs -> template designs -> doctrines. The reason for this is that you need spirits to increase your army exp gain and reduce land doctrine cost(best taken early to maximize gains) and make template designs free. Tank designs because you need to be able to build your desired tank before you can even worry about putting them in a template. Template designs because you need to be able to put your tanks in good divisions before you can even worry about buffing your divisions with doctrines. Lastly, doctrines because that's the final cherry on top to make the good divisions you've designed even better. Doctrines without good divisions to buff are worthless - zero multiplied by 100 is still zero.
As long as you have green air, some CAS, and good tank designs and templates, beating France should be easy as long as you micro your tank divisions and don't use the battle planner. Look for places you can break through the lines and start snaking, all you usually need to do to capitulate France is take Paris, Calais, and one other victory point.
Lastly, economy. If you followed all the rest of the advice and have good designs and still can't break through, my guess is you built civilian factories for too long (this is sometimes called civ greeding) and don't have enough equipment produced. You really want to start building military factories at least by January 1938 so you have time to build up production efficiency. You can start building mils as soon as January 1937 if you really want to make sure you have plenty of equipment. Build synthetic refineries only after you have built up a large base of military factories, you delay your factories by too much if you build refineries first.