Ok so do a lot of poles in a strait line and across the diagonal and you can put one pole on the ground in the middle of the ring and trot on the diagonal but slice the pole in half,and that helps the horse to know where his feet are
Straightness will come in time. I wouldn't aim for straightness right away as it's actually quite difficult for a young horse to achieve. For suppleness, you need both rhythm and relaxation. The most common reason a young horse lacks suppleness is tension, and unbalanced-ness.
Given there are no underlying physical problems, tension will usually resolve itself when a horse becomes more confident and used to riding. Clear, precise aids coupled with rewards (breaks, scratches etc) for improvements allow the horse to learn better and more confidently.
A lack of balance and rhythm usually starts to improve more when the horse gets fitter and used to a rider's weight. Balance will also help to bring about relaxation. Exercises such as circles and serpentines will help develop basic balance. Polework is excellent for developing it further. There are some fantastic pole exercises online.
Before you can work on straightness, other than rhythm and relaxation (which should be done first), you also need to teach the horse to accept aids. Ensure a good response through all aids. Again, clear, precise aids with rewards for improvements will help here.
Lastly, before straightness, you may have to develop a horse's impulsion. This is when the horse has the capacity to lift itself and go forward with energy. It does not mean running away. Impulsion can be a little bit tricky, depending on the horse. However, if the first three are in place, it will make this a lot easier. I would recommend working with a training at this point.
Just general exercises for young green horse will be an eventer in the future so to teach suppleness and straightness
I think that Caoimhe's question is essential : what goal do you need to achieve with your horse ? And how young is he ?
Do you have a particular aim in mind?