You should pay specific attention to the basics in GMAT, such as basic math concepts and formulas, basic logic reasoning, general reading comprehension, vocabulary, etc. Then use the GMAT questions to test what you have learnt.
I am the only one here who doesn't have a say on your plan. However, it can’t be wrong to tell you to lay a solid foundation first.
NNs say that reading is the key. If your vocabulary is relatively poor as you mentioned, you can practice on a few readings. If you can't read them through smoothly, it does no harm to spend some time on V, since you have more than 4 months to prepare for G.