Any new cockatiel that you want to handle must be comfortable with being in your close presence.Those that aren't comfortable and not submissive at best will avoid you and worst will probably seek to bite you.
We have a re homed bird named Banjo ( my niece's bird ignored since she started high school and uni) who did nothing but bite and draw blood when the sister or mum put hands in the cage to feed and water the bird.They have had the bird over ten years .At the rare times when my niece handled Banjo he would not bite her.
Both sis and my mum no longer have the time or situation to further care for Banjo.
My wife and I now have this bird and we changed him in less than six months.
We have a lot of time-wife works only part time and I am retired.
We started out by talking softly to Banjo every time we passed the cage.After two weeks we opened his cage door and allowed it to be open most of the day.
To explain further we have another hand reared from a baby cockatiel Matey, now 24 months plus that free ranges from a open cage so he comes back to his cage to sleep and eat.
Eventually we coaxed Banjo out of his cage.He just sat on it for a fortnight and after a time he would fly over to Matey's cage and after a month or so of that ,we re housed Banjo along side Matey in a much bigger big cage.
Six months on, a once scared biting,blood drawing bird now is much happier and comfortable enough to leave the cage and jump on our hands and sit on our shoulders and steal bits of toast crumbs from our breakfast plates. Banjo is 11 years plus and does not fly strongly due to his being caged for most of that period.
However he is strengthening week by week. He is certainly more interactive and reacts (bird talk) when we speak to him.
As far as toys go my birds prefer things they can chew and destroy.We put empty kleenex tissue boxes on the cage floor and in strategic places in the house. The bird reduce them to pulp with in a week or two. Its the nature of these little blokes to chew so place boughs of a harmless tree in the cage and let them at it. Bottle brush an Aussie native tree is their favourite.
Most female cockatiels can be ID by the bars - like sergeants stripes on the underside of the tail-which designates the female
in most colours except yellow.This is not reliable method until a couple of years old.
The message here is to prove to him/her there you are not a threat. You must talk soothingly and move extra slowly in the birds presence .Normal motion(speed) is seen as an attack and you bird is programmed by nature to react and either bite or fly away.
So long as you are persistent you will have a wonderful affectionate companion in good time but you MUST put in the time and effort.