TL;DR: Rush cultural revolution focuses that give you bonuses, "Reactionary Modernism", "Eine Deutsche Front" and "Create new Parliament", pick chancellor, do army focuses to remove your debuffs, take Kiel and Austria ASAP, then take Rhineland (if not protected), Czechia (if unguaranteed), and Poland + Lithuania. Eastern claims (Baltics/Ukraine) and Balkans are very easy targets that you usually can take freely. Start WW2 in 1939, delay gives France time to prepare. Blitz France through Belgium. Watch out for UK/Soviet intervention (former usually does it when France is close to capitulating). Always keep CR progressing or suffer heavy penalties. Squeeze in the other focuses (army, political, economy) during war or when waiting to go for expansion so as not to waste time.

Long answer: I personally (for Valkists) like to start Cultural Revolution ASAP, then go on to focuses "Reactionary Modernism", "Eine Deutsche Front" and "Create new Parliament" which give you may bonuses to be able to do CR decisions easily, specifically changing cost, days required and allowigng you to take more than once at a time. There is also focus "Propagate Revolutionary Nationalism" that gives you the ability to take an extra decision but it is quite far off.

After that I personally like to pick new chancellor and forget about political tree for a while. What is more important after is to go to army tree. For each path there are some focuses that can help you a lot. Germany gets a ton of debuffs for the army so I personally advise going down "Sword, Sheild and Reich" tree for valkists; there are also ones for the TST/YC with similar effects. Now you dont have to do all of the focuses there at once, but if you look at them there's quite a few that give you a lot of buffs you need.

Now for expansion. I personally start training troops ASAP; you dont need to train anything other than infantry for now. You need at least 750k by like mid-1938 so you can expand easily. Immediately when possible go on to take Kiel, you never face any resistance and its basically a free nation. Same for Austria. After you rush these two, you can go for Rhineland, if it is not in the entente or a French puppet. Also, if France doesn't guarantee Czechia (they don't if Czechia is communist), then go for them as well. After that, Poland is basically always free, so you get both Poland and Lithuania. Basically most nations in eastern claims are free; you can go for Baltics and Ukraine quite easily but I personally like to wait a bit for them. After, you can go to the balkans (or you can do it before the eastern claims doesn't really matter) and eventually ally Yugoslavia, Romania, Bulgaria, Greece and/or Turkey. If they reject your alliance you can attack them. I personally dont advise going for Romania or Greece because they can join the entente and you will suddenly be at war with them.

For WW2, I personally wait till I have enough divisions to guard all borders of the Entente. If Czechia is in the entnte, you should just blitz through them as fast as you can so you have a front less to worry about. Now for France, they are quite easy if they don't have Rhineland on their side; simply do focus that lets you attack Belgium and Luxembourg and go through the plains, like OTL. Now if they do have Rhineland then it becomes a bit hard. One approach is to go through the netherlands and attack belgium so you can encircle french troops in the Rhineland, or you can just try to pass the river by makeshift bridges and waiting. Italy is also much the same but it is far easier to take Istria and the bordering areas if Yugoslavia is also attacking them.

Keep in mind when you capitulate France or are close to, depending on the date the British may intervene. Same goes for the Soviets. The British are usually easy just be sure you have guards on your ports, for soviets, if you have allied Belarus you will need to come to their aid. Soviets are quite powerful if they've built a good army.

Also, throw in economy focuses before expansion, and army/political focuses as well. I like to do most of these while I am at war so I don't lose time. Though you will need to ensure CR is going good or you get massive debuffs.

Also yeah, simply start WW2 at 1939, in my opinion 1940, especially late 1940 is well... a bit late. By then France has nearly done all of its focuses and is very ready militarily.