I'd suggest that the first thing you need is a syllabus - it's this that will help you decide what to teach, whereas the type of sites you mention deal mainly with the second step : how to teach it. I'd suggest the
Oxford University Press site. They publish on-line the syllabuses for all their books( go to the Teacher's Club -you have to register but it's free), and they're undoubtedly amongst the best in the field. It doesn't make sense to try and reinvent the wheel if experienced and qualified engineers have already spent half their working lives doing it for you. Choose one relevant to the age group, type of learners you have and follow it. That gets decision one out of the way, and at that point you can focus on how to present and practise the language points in the syllabus. The
OUP site will also provide you with a variety of sample materials, but if you want to invest a bit, why not divert some of the funds to getting the books? Certainly though, at this point sites like
onestopenglish will be useful.
Onestopenglish is the Macmillan site and although you have to pay a certain amount for full access it has a wealth of information, including tready made lesson plans. I'd say that in your situation it's worth it, even though you can get other similar material elsewhere - no single site is going to keep you going with all your classes for a whole year. Invest in one and get the rest free elsewhere. For flashcards, for example, I always use the ones on this site or
mesenglish. For other free sites try
Teaching English ,
eslkidsstuff, and
eslbase.
they all have lesson plans, worksheets, activity descriptions etc. That's just a selection, and they'll lead you on to many more if you follow the links they include - and of course the ones featured on this site.