I am a LLM veteran, as i get quickly bored starting in higher leagues.
From my experience there are a few key things you can do to progress quickly some of which have already been mentioned
1. Arrange friendlies in preseason to raise funds
2. play direct football - tiki taka will not work due to the poor quality players and worse pitches
3. loan players at 0% wages - aim to strengthen your first 11 but if you can only get 2 who can make your starting 11 fill your loan quota to increase your strength in depth (these players are free make the most of them)
4. find a parent club ( in the past boards have been reluctant until you turn pro to make such links but worth a try)
5. take the FA cup extremely seriously!!!!!! it offers huge financial benefits if you can get through past the first round
6. do not spend any money on players until you get to the championship, there is almost always an alternative on the free or loan market
7. do not exceed your wage budget, you will end up in a debt spiral you will never escape
8. switch any transfer budget across to wages
9. tactics have a greater impact than players at this level, find one that works with the style of players you buy (i.e. no point using route 1 target man tactics if you centre forward is jermaine defoe). always have a back up tactic ( i tend to use the same/similair formation but switch up tempo and mentality).
as for players on fm15 i have just started unemployed and got the hyde job so only played 6 games, but players that are doing well for me;
sergio menisio
david easthorpe
d'arcy o'connor
henoc mukendi
also may sound stupid (but i have had to advise a few friends already) but when searching for loans change the filters so realistic transfers is not ticked and tick realistic regular loans
hope this helps