I myself have just started a game as Blackpool, and in all honesty for a team who have just come into the league they have a decent squad. And I'm confident you could stay up with the current team, I'd say opt for some younger players, and hopefully in 2-3 years they'll have produced into first team players.
If you're wanting to spend, priority would be a GK.
After a quick look, I'd opt for either Roy Carroll, David Ospina, Lars Hirschfeld or Didier Ovono.
All would come to Blackpool, and you should be able to get any with your budget.