Stick to a domain. Try to expertise in one topic at a time. Also read reviews before getting enrolled. Some courses also offer a trial part. Also if you can access the resources for free you need not compulsarily pay in for a certificate as you can mention the skill you've gained in cv instead of putting it up in certification. The knowledge gained behind is what really matters.
You check out Harvard Online Classes as some of these courses are actually free.
Coursea. But, if you do free course from there they will not give you a passing certificate.
You can try taking online training from Internshala or websites like this. You can learn skills and get a certified training also that you can use to boost your CV
There's Coursera, Udemy, Shaw Academy and many others.
I suggest you can simple search courses on YouTube. There are tons of free courses which won't give you certificates, but knowledge for sure.
You can apply for financial aid on Udemy and learn amazing courses free of cost.