when you say "a lo mejor..." or "a ver si..." should you use subjunctive?
Not necesary you should use a subjuntive, only if you talk in past tense, especifically : antepreterito, for example with: " a lo mejor"
... oh my God I am thinking the best way to explain it... First of all, this expression : " a lo mejor" express a possibility I think it is like " maybe" , but if you talk about one possibility or desire in the past, that in the present is already imposible, you must to say, something like:
A lo mejor si hubiera ahorrado lo suficiente, ahora podria viajar a la olimpiadas.
Maybe if I had saved enough money, now I could travel to the olimpics games.
You have to write "si" "if" because that was a possibility in the past but not anymore.
But if you talk about the future, but a near future, no need subjuntive. For example:
A: Vas a la fiesta manana? Are you going to the party tomorrow?
B: No se, a lo mejor voy. I don't know, maybe I am going to.
A: Que vas a estudiar cuando seas grande? What are you going to study when you grown up?
B: A lo mejor estudio ( o estudiare ) medicina. Maybe I study ( will study) medicine.
with " a ver si " i think is simplier:
Vamos a ver si manana podemos salir un rato.
Voy a ver si puedo ir temprano manana.
It is always for future.
I hope this little explanation could help you in your request.
a lo mejor si hubiera ahorrado lo suficiente, ahora podria viajar a la olimpiadas. -