I need help with what plants to choose. each year I spend a fortune just for the slugs to eat, or for them to die because soil is bad I need to know what plants I can buy that will survive both problems
Sort your soil first. I have just bought 3 bags of well rotted horse manure @ £1.20 each. My soil is already looking better.
For slugs, use nematods which work well in warmer weather if you are not on heavy clay. If you are on heavy clay, you could try small sharp gravel, used as a mulch. Put used coffee granuals, broken egg shells or wood ash around plants also work sometimes.
The comments about improving soil are right. You want to keep it on the dry side. Damp soil just encourages slugs: in the dampest part of my garden I have a plague on the driest part I have none.
Nematodes may work but it is still too cold for them and you need to apply it all the time and they cost loads. Egg shells, coffee and wood ash are urban legends and do nothing to stop slugs. Wood ash is harmful to acidic loving plants! So ignore those as all you will do is waste your time.
Best thing I ever used was slug pellets - kills loads and few of my plants have damage and seedlings actually make it.