This is often a chicken-and-egg scenario for many people new to the employment world.
How much stock a hiring manager will put in coding test sites is such a wild variable that it almost makes this question un-answerable (see the calls for 'too opinion based')
For me, I would consider those coding sites - but I'd put more stock in say whether you had a part-time job.
I care more about your work ethic than your skills and experience - because as an entry level worker (even if you have a degree) as far as I'm concerned, you have none.
Things you can do though, if you can't get an interview - look at places like Fivver (I think) where people submit requests for work, with a dollar value. Now, I've not used it and from what I understand there is a lot of shall we say 'low-balling' - but a completed, delivered coding project for a paying customer is worth 20 times what a code challenge website is worth to me.
Internship at a company - even an unpaid one, "I'm looking for work experience as a Software Dev" - some companies might have some odd-job code projects that they don't have the manpower to deal with at a full Software Dev rate, but a recent graduate could probably tackle. Even better if it is a paid internship with the possibility of a full-time role after completion.
I trust this gives some ideas - essentially, when you have no experience - what I want to know is that you will work hard and have a willingness to learn. Everything else happens with time.