I would gently try to dissuade one from learning fixed phrases but try to instead use vocabulary for learning a lot of vocabulary, and then as quickly as possible finding listening/reading material and then finding where your grammatical weaknesses are. But, if you really want to go for phrases, feel free to ignore what I say, because what worked for me may not at all work for you … as motivation seems to be better than any “magic bullet” method which may or may not exist…
I would also bear in mind that there are many different ways to do flashcards for Chinese because of the disconnect between reading and listening. There are technically 6 ways to do flashcards for single words/phrases (assuming no real audio is used as a prompt), which you may already know about but I repeat here because I think this guides what courses you should take/ self-create ( if you are so inclined).
Using 我 = I = wo3 as an example… (If you are using pinyin for pronunciation…I do not know about other forms, so if this doesn’t apply I am sorry).
You could have
1.Prompted with 我 tell me I (testing on your ability to read Chinese text in English)
2.Prompted with 我 tell me wo3 (testing primarily on your ability to read out loud in Chinese)
3.Prompted with wo3 tell me I (With assumptions on you knowing exactly what each sound and tone in pinyin sounds like… tests primarily single word “listening”, but using 7 properly is better)
4.Prompted with wo3 tell me 我 （Useless, just testing your ability to use a Chinese input keyboard)
5.Prompted with I tell me 我 （Tests on pronunciation without enforcing tones, as well as limited character recognition…probably the closest thing to practicing written Chinese on Memrise)
6.Prompted with I tell me wo3 (Tests on pronunciation with tones, perhaps helps your ability to come up with single word translations faster…so “speaking”)
7/. Also, some courses are audio only which are useful too, but I think there are caveats to using them properly and incorporating them into your study routine (which I could go into if you are at all curious) . Some of the weaknesses of these are the nature of the multiple choice answers here which I think make them too easy. So you have to exercise self-control here to not peek at the answer until you retrieve it in your mind yourself.
Personally, I have found the HSK courses to have some errors and flaws, but overall have been very helpful. (The Ben ones, as well as some others like Drew’s HSK 6, and Niallo’s HSK Complete, some of the Audio only ones)
Personally, I have found 1. the most useful for helpful for getting me to the point where I can read Chinese material and begin to find my grammatical weaknesses/guess meaning of new grammar patterns. I found that 2. is used in a lot of Memrise courses but I found it does not help me retrieve this information in a timely manner to help me with developing “output” as in writing/speaking. I found that 5 is very helpful towards getting me to this goal of composing my own sentences, as well as trying out and using my Memrise-learned vocabulary. I find 7 useful, but I find it useful only after I have the knowledge of 5, as I find they use similar types of “mental muscles”.
The new approach I have been using to learn vocab/chengyu uses “tiers” of learning where I learn the flashcard method in 1 ==> 5===> 7, which eventually gets me to being able to hear the word and know its English meaning, as well as thinking of an English word and being able to pull out the Chinese word into my pinyin input. I use Italki partners to then correct my grammar, and I correct theirs. So I get practice on phrases and grammar this way.