I am a self-studier. I additionally attend courses, but most of the time I sit in my study and do exercises from the very recommendable book called “Grammar in use” or for Spanish
“Con Gusto”. I listen to the English radio every morning on my way to work and to Spanish audio books for a better understanding and I attempt to expand my vocabulary knowledge continuously by repeating those every day with the old school vocabulary cards; in my opinion, the best way how to do it.
I only attend the Spanish course to have an opportunity to use it in practice. I have got lots of English speaking friends, but unfortunately only a hand full from Spain or South America. Normally, I am already much further in the book, but repetition is everything.
My tip how to learn and become confident in a foreign language is definitely to keep it rolling. My aim is to at least work on it one hour a day, but others say that half an hour or at least 10 minutes were enough as well. I assume that depends on your ambition.
Being fit in the use of grammar is recommendable. First language speakers can understand you anyway, but in some cases expressions differ and misunderstandings could occur, what needs to be shunned.
If you lack of money to pay extern courses you just need to have a look on the internet. There are thousand opportunities to do exercises or inform you about a specific grammar rule.
I am really fond of “Babbel”. The price is low and depends on your duration; three month, six months, nine months and so on. The exercises are easy at the beginning and become more and more difficult; but on the other hand, there are lots of really good explanations and examples to get used to it.
Additionally, Babbel provides a forum where you can get your texts or other exercises corrected and you can find friends to communicate.
Generally, it is helpful to adapt yourself completely to the foreign language. For example, change your Mobil phone language to the one you would like to be confident in, write your shopping list in it and try to think in your favorite idiom. All those tips and tricks really help me to enhance my skills and knowledge.