An other "book" that you could buy out of your loose change is a journal / dairy. Talking to yourself will be a great way of recording and recognising your achievements as you go. Something like:
Dear Greek learning diary,
Today I learned the words for "plate" xxxxxx. Xxxxx is used with the verb yyyyyy. With the verb xxxxxxx, it takes the form xxxxb so I can say yyyyyp xxxxxb.
By synthetically (1) analysing (spelling out) what you see, then by (2) engaging in some higher-order thinking using whatever grammar you know to (3) create something, you might find the learning process more rewarding. So, also with questions:
Dear Greek learning diary,
I see that the word for "plate" has three syllables xxxxx in the dictionary, but has four syllables xxxxxx in the NT text xxxxx xxxxx xxxxx xxxx xxxxx (Matthew 23:25). I really don't understand why the word for "plate" is longer by one syllable longer, when used in the NT, than it is in the dictionary. The difference appears to be that there is a ccc after/between/before the ddd.
You won't necessarily be able to answer your own questions, but rationalising ignorance makes it more manageable emotionally. In doing that sort of break down of your things you have diffuculties with, you will have gathered and recorded data from a number of sources. You will have recognised both relatedness and difference. You will have thought about what the nature of the difference might be. That process of reduction may or may not lead to the correct interpretation of WHAT or WHY there is a difference, but it will have been a step in the right direction (a step towards personal engagement with the language). So too with assumptions, catch them as they slip past the gate guards:
Dear Greek learning diary,
I think that the word xxxxxx for "plate" could also mean "bowl", because of such and such (unrelated) reason.
Your natural inclination will be to make some broadreaching assumptions to make things more manageable. Such overextensions of grammar or word meaning are very common, and will in most cases self-correct as your knowledge and experience increases. Writing them down however, will allow you to more easily identify them as logical infrences, and to let you be less possessive of them, when it is time to give them up.
[I used the diarying method for a long time, but without the "Dear diary..." personalisation.]
Besides the diarying, you should be aware of what you are learning, when you learn Greek. There is the form of the language, that needs to be decoded - the foreign looking alphabet, the complexities of the verb and noun in their many forms, but such decoding is not decoding into English, it is decoding into Greek. Let me explain a little.
Greek has a system of grammar which works in abstracto. Various theoretical constructs work together to form the Greek language. Some people who learn the language, decipher from the form of the Greek language to English, then construct meaning soley using their mother-tongue language processing skills. While that is common, it is not necessarily the best, and it won't necessarily result in learning the language. Two alternatives to that are analysing the grammar and learning to think in the language through some sort of kinesthetic method.
The first type of learner, somebody who decodes the form of the Greek directly to English will say, "I understand αὐτῷ. It means 'to him' or 'to it'." The sevond type of learner, developing the analytical approach, one might say at the outset, "I understand αὐτῷ, because I know it is the dative singular masculine form of αὐτός." That however is only a means to reference what it is in the abstract grammatical system of Greek. The desired goal of learning Greek, is to know what a dative does in the language, not only to identify it - think of the difference between a natural history museum (statically analysed forms), and a zoo (forms in a "natural", but contained environment, interacting with each other in limited ways that are "typical"). Seeing similar things in the language lined up side by side lets us see some similarities that we may not notice otherwise. In the process of decontextualisation, however, a lot of contextual information is lost. Fads and fashions in zoo construction and grammar presentation are sort of parallel in their preferences - the decontextualised compartmentalism accompanied my a plaque of scientic explanation and background information of a century ago has given way to interactive, impressionistic or experiential approach in both things, relecting the changing preferences of the ages. Buying another grammar written within the same general mindset will only add very little more than paper to your library.
How while it may be possible to either see the long explanations described on the plaque acted out in the wild, or to see the typical behaviours of certain word forms occuring in a text, the texts that you will be engaging with are much more than that. They typical behaviours that you might expect - foraging, hunting, nesting, mating and rearing - are only typical in so far as they are abstracted. In terms of Greek, that is the many social functions that language performs. To some degree they correspond to the forms of the Greek that you will decode, but you will find that the way the language works to express meaning is so much more than the forms, and more than the grammar. Using evermore educated commonsense - engaging a practical and practicing brain - is usually a good thing.
Set some learning goals - both big ones and immediate ones - and yse them to structure the other things of interest that will inevitably come up that you don't know about yet. Some goals might be:
- To learn your favourite verse or phrase in Greek,
- To finish a chapter of a textbook,
- To learn 3 new letters of the alphabet each day this week,
- To listen to the same passage of Greek over and over till it seems familiar,
- To record your own reading, to self-check it, or
- To write out a phrase, a list or a table that you are trying to master.
Good luck in your endeavour.